chore: update PR checklist

Improve the PR checklist to make it more clear and explicitly ask
contributors to run the automated checkstyles.

Signed-off-by: Riccardo Mancini <[email protected]>

.github/pull_request_template.md

@@ -15,16 +15,20 @@ Certificate of Origin and signing off your commits, please check
 
 ## PR Checklist
 
+- [ ] I have read and understand [CONTRIBUTING.md][3].
+- [ ] I have run `tools/devtool checkstyle` to verify that the PR passes the
+  automated style checks.
+- [ ] I have described what is done in these changes, why they are needed, and
+  how they are solving the problem in a clear and encompassing way.
+- [ ] I have updated any relevant documentation (both in code and in the docs)
+  in the PR.
+- [ ] I have mentioned all user-facing changes in `CHANGELOG.md`.
 - [ ] If a specific issue led to this PR, this PR closes the issue.
-- [ ] The description of changes is clear and encompassing.
-- [ ] Any required documentation changes (code and docs) are included in this
-  PR.
-- [ ] API changes follow the [Runbook for Firecracker API changes][2].
-- [ ] User-facing changes are mentioned in `CHANGELOG.md`.
-- [ ] All added/changed functionality is tested.
-- [ ] New `TODO`s link to an issue.
-- [ ] Commits meet
-  [contribution quality standards](https://github.com/firecracker-microvm/firecracker/blob/main/CONTRIBUTING.md#contribution-quality-standards).
+- [ ] When making API changes, I have followed the
+  [Runbook for Firecracker API changes][2].
+- [ ] I have tested all new and changed functionalities in unit tests and/or
+  integration tests.
+- [ ] I have linked an issue to every new `TODO`.
 
 ______________________________________________________________________