Chore: updated sdk README

[bvotteler]

Resolves #178

Updated README with the following changes

• updated install instructions
• fixed outdated npm package name
• more clearly separated instructions as a consumer of the sdk vs building
• added contributing section

Bonus:

• added package-lock.json to stop CI's SDK test step from failing
• added missing parameter in one of Hello Bitcoin's commands

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Name	Status	Preview	Comments	Updated (UTC)
bob	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 14, 2024 9:03am

[derrekcoleman]

Thank you! Agreed with all of your adds to the language in the README. I know we'll all appreciate the SDK CI passing from now on, too.

@nud3l, please merge.