docs: clarify fallback when no good first issue labels are open (AI-assisted)

[qkal]

Summary

Updates CONTRIBUTING.md to clarify what first-time contributors should do when there are no open good first issue labels:
pick a small docs/bug issue and leave a quick comment to claim it.

Why

This helps new contributors avoid getting blocked when the good first issue queue is empty.

Testing

Docs-only change.

[qkal]

This is my first open-source contribution to OpenClaw, so feedback is very welcome. I kept this PR intentionally small and focused.

[greptile-apps]

Greptile Summary

This PR updates a single paragraph in CONTRIBUTING.md to improve the new-contributor onboarding experience. It converts the generic GitHub Issues link into a pre-filtered link pointing directly to open good first issue labeled issues, and adds a fallback sentence advising contributors to pick a small docs or bug issue and leave a comment when no labeled issues are available. The change is accurate, well-scoped, and consistent with the project's existing contributor guidance tone. No issues found.

Confidence Score: 5/5

This is a safe docs-only change with no code, logic, or functional impact.

Single-paragraph documentation edit with no code changes. The filtered GitHub URL is correctly encoded, the added guidance is accurate and helpful, and no custom instruction rules are violated.

No files require special attention.

Important Files Changed

Filename	Overview
CONTRIBUTING.md	Single-paragraph update converting a plain issues link to a filtered 'good first issue' link and adding a fallback suggestion for new contributors.

_{Reviews (1): Last reviewed commit: "Docs: clarify first-contribution fallbac..." | Re-trigger Greptile}

[Copilot]

Pull request overview

Updates contributor guidance to reduce onboarding friction when no good first issue items are available, by directing first-time contributors to claim a small docs/bug issue instead.

Changes:

• Replaces the generic “check good first issue labels” guidance with a direct link to the filtered good first issue query.
• Adds fallback instructions to pick a small docs/bug issue and comment to claim it when none are open.

[fabianwilliams]

LGTM — reviewed code, tests, and approach. Clean implementation.