Add a CONTRIBUTING.md with PR expectations

[johnmcollier]

Summary

Add a CONTRIBUTING.md at the repository root so newcomers know how to open a pull request.

Acceptance criteria

Create CONTRIBUTING.md with:

• A short intro (1–2 sentences) that this is the rhdh-parasol python-app playground
• How to propose a change: fork or branch off main, open a PR
• PRs must include a description of what changed and why
• Issues should be linked from the PR when one exists

No other files need to change. Keep it under ~40 lines. Markdown only, no extra tooling or CI.

[fullsend-ai-triage]

🤖 Finished Triage · ✅ Success · Started 7:58 PM UTC · Completed 8:00 PM UTC

Commit: f545dd0 · View workflow run →

[fullsend-ai-triage]

The acceptance criteria are clear and self-contained — this is ready for implementation.

Proposed test case

- Verify CONTRIBUTING.md exists at the repository root
- Confirm it is under 40 lines
- Check it includes: project intro, fork/branch workflow, PR description expectations, and issue-linking guidance
- Confirm no other files are modified

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Next steps:

• /fs-code — agent creates a PR to implement this issue
• /fs-code <your instruction> — agent implements with your specific guidance