docs: add contribution guidelines

[mojomex]

PR Type

• Improvement

Related Links

• Inspired by comma.ai's openpilot

Description

Add contribution guidelines to Nebula. This allows easier contributions from the community and provides a clear set of rules and expectations we can refer to.

Pre-Review Checklist for the PR Author

PR Author should check the checkboxes below when creating the PR.

• Assign PR to reviewer

Checklist for the PR Reviewer

Reviewers should check the checkboxes below before approval.

• Commits are properly organized and messages are according to the guideline
• (Optional) Unit tests have been written for new behavior
• PR title describes the changes

Post-Review Checklist for the PR Author

PR Author should check the checkboxes below before merging.

• All open points are addressed and tracked via issues or tickets

CI Checks

• Build and test for PR: Required to pass before the merge.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[drwnz]

Mostly minor (some more style-based that could go either way), with one or two must-fixes in there, but generally excellent.

[mojomex]

@drwnz Thanks for the many suggestions! I applied them all. Please re-review when you find the time 🙏

[drwnz]

Nice ;)