Add Contributor License Agreement

[stasimus]

Adds CLA.md and a short Contributing section in the README.

The same text lives in a gist (https://gist.github.com/stasimus/b30d43b6024e233536cf4728a0edd022) so CLA Assistant can use it once an org owner installs the app and links the repo on cla-assistant.io.

Summary by CodeRabbit

• Documentation
  • Added a Contributor License Agreement outlining contribution rights and licensing.
  • Added contribution guidelines explaining the agreement requirement before pull requests can be merged.
  • Included instructions for completing the agreement through the signing assistant.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 0df7cbb7-5d6e-4ac8-86e1-62dfec24ebd8

📥 Commits

Reviewing files that changed from the base of the PR and between dde27b9 and 50c6b95.

📒 Files selected for processing (2)

• CLA.md
• README.md

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📝 Walkthrough

Walkthrough

Added a Contributor License Agreement and documented the required CLA signing process for external pull requests.

Changes

Contributor licensing

Layer / File(s)	Summary
CLA terms and contribution workflow CLA.md, README.md	CLA.md defines permitted contribution use, project ownership, maintenance, and contributor ownership. README.md requires external contributors to sign the CLA before pull requests can be merged and describes the CLA Assistant process.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested reviewers: mr-git

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch add-cla

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