add oss documents

* add CONTRIBUTING.md, CODE_OF_CONDUCT.md and pull_request_template.md
* move template description to CONTRIBUTING and add contributing to README

.github/pull_request_template.md

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+## What to do  
+
+## Background  
+
+## Acceptance criteria  

CODE_OF_CONDUCT.md

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+
+# go-hubspot Code of Conduct
+
+## Our Pledge
+
+We as members, contributors, and leaders pledge to make participation in our
+community a harassment-free experience for everyone, regardless of age, body
+size, visible or invisible disability, ethnicity, sex characteristics, gender
+identity and expression, level of experience, education, socio-economic status,
+nationality, personal appearance, race, caste, color, religion, or sexual
+identity and orientation.
+
+We pledge to act and interact in ways that contribute to an open, welcoming,
+diverse, inclusive, and healthy community.
+
+## Our Standards
+
+Examples of behavior that contributes to a positive environment for our
+community include:
+
+* Demonstrating empathy and kindness toward other people
+* Being respectful of differing opinions, viewpoints, and experiences
+* Giving and gracefully accepting constructive feedback
+* Accepting responsibility and apologizing to those affected by our mistakes,
+  and learning from the experience
+* Focusing on what is best not just for us as individuals, but for the overall
+  community
+
+Examples of unacceptable behavior include:
+
+* The use of sexualized language or imagery, and sexual attention or advances of
+  any kind
+* Trolling, insulting or derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or email address,
+  without their explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+## Enforcement Responsibilities
+
+Community leaders are responsible for clarifying and enforcing our standards of
+acceptable behavior and will take appropriate and fair corrective action in
+response to any behavior that they deem inappropriate, threatening, offensive,
+or harmful.
+
+Community leaders have the right and responsibility to remove, edit, or reject
+comments, commits, code, wiki edits, issues, and other contributions that are
+not aligned to this Code of Conduct, and will communicate reasons for moderation
+decisions when appropriate.
+
+## Scope
+
+This Code of Conduct applies within all community spaces, and also applies when
+an individual is officially representing the community in public spaces.
+Examples of representing our community include using an official e-mail address,
+posting via an official social media account, or acting as an appointed
+representative at an online or offline event.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported to the community leaders responsible for enforcement at
+[INSERT CONTACT METHOD].
+All complaints will be reviewed and investigated promptly and fairly.
+
+All community leaders are obligated to respect the privacy and security of the
+reporter of any incident.
+
+## Enforcement Guidelines
+
+Community leaders will follow these Community Impact Guidelines in determining
+the consequences for any action they deem in violation of this Code of Conduct:
+
+### 1. Correction
+
+**Community Impact**: Use of inappropriate language or other behavior deemed
+unprofessional or unwelcome in the community.
+
+**Consequence**: A private, written warning from community leaders, providing
+clarity around the nature of the violation and an explanation of why the
+behavior was inappropriate. A public apology may be requested.
+
+### 2. Warning
+
+**Community Impact**: A violation through a single incident or series of
+actions.
+
+**Consequence**: A warning with consequences for continued behavior. No
+interaction with the people involved, including unsolicited interaction with
+those enforcing the Code of Conduct, for a specified period of time. This
+includes avoiding interactions in community spaces as well as external channels
+like social media. Violating these terms may lead to a temporary or permanent
+ban.
+
+### 3. Temporary Ban
+
+**Community Impact**: A serious violation of community standards, including
+sustained inappropriate behavior.
+
+**Consequence**: A temporary ban from any sort of interaction or public
+communication with the community for a specified period of time. No public or
+private interaction with the people involved, including unsolicited interaction
+with those enforcing the Code of Conduct, is allowed during this period.
+Violating these terms may lead to a permanent ban.
+
+### 4. Permanent Ban
+
+**Community Impact**: Demonstrating a pattern of violation of community
+standards, including sustained inappropriate behavior, harassment of an
+individual, or aggression toward or disparagement of classes of individuals.
+
+**Consequence**: A permanent ban from any sort of public interaction within the
+community.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage],
+version 2.1, available at
+[https://www.contributor-covenant.org/version/2/1/code_of_conduct.html][v2.1].
+
+Community Impact Guidelines were inspired by
+[Mozilla's code of conduct enforcement ladder][Mozilla CoC].
+
+For answers to common questions about this code of conduct, see the FAQ at
+[https://www.contributor-covenant.org/faq][FAQ]. Translations are available at
+[https://www.contributor-covenant.org/translations][translations].
+
+[homepage]: https://www.contributor-covenant.org
+[v2.1]: https://www.contributor-covenant.org/version/2/1/code_of_conduct.html
+[Mozilla CoC]: https://github.com/mozilla/diversity
+[FAQ]: https://www.contributor-covenant.org/faq
+[translations]: https://www.contributor-covenant.org/translations

CONTRIBUTING.md

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+# Contributing
+
+First off, thank you for considering contributing to go-hubspot.
+
+## Reporting bug & Feature request
+
+If you've noticed a bug or have a feature request, please make an [issue](https://github.com/belong-inc/go-hubspot/issues).  
+Some issue contents are being or have been fixed, so it is recommended to check for similar issues.  
+
+## Code change flow
+
+If the bug or feature request is something you think you can fix by yourself, please follow the steps below to change the code.
+
+### Fork & create a branch
+
+Fork repository and create branch with a descriptive name.  
+
+### Implement fix or feature & run lint and test
+
+When making changes to the code, keep in mind that this is an externally used library.  
+Give variables and functions etc. easy-to-understand names, and avoid unnecessary exports. In addition, additional comments on why you did it would be helpful to reviewers and users.
+
+You will also need to lint and test your changes. Make sure to run `make lint` and `make test` when the fix is complete.
+
+**Be careful not to put your environment's api key or oauth information in git!**
+
+### Make a pull request
+
+When you have finished modifying and testing the code, please create a pull request with a description of the content. The lint and test will be executed by Github actions, but it's the same confirmation as local execution, so if it's already executed, no problem is expected.
+
+When creating a pull request, we ask for the following items to be included. The items are described in the template.
+
+- What to do  
+  - Please describe the purpose and what changes of this pull request.
+  - If you have any reference links, please include them.
+
+- Background  
+  - Please describe why you need to make this modification.
+
+- Acceptance criteria  
+  - Please describe what can be considered complete.
+
+### Merging a pull request (maintainer only)
+
+A PR can only be merged into main by a maintainer if:
+- It is passing CI.
+- It has been approved by maintainers.
+- It has no requested changes.
+- It is up to date with current main.

README.md

@@ -208,3 +208,8 @@ fmt.Println(customDeal.CustomA, customDeal.CustomB)
 |API key      | Available |
 |OAuth        | Available |
 |Private apps | Not Implemented |
+
+# Contributing
+
+Contributions are generally welcome.  
+Please refer to [CONTRIBUTING.md](CONTRIBUTING.md) when making your contribution.