docs(READMD.md): add star history to README

[HankyStyle]

Description

Add star history to README

Checklist

• I have read the contributing guidelines

Code Changes

• Add test cases to all the changes you introduce
• Run uv run poe all locally to ensure this change passes linter check and tests
• Manually test the changes:
  • Verify the feature/bug fix works as expected in real-world scenarios
  • Test edge cases and error conditions
  • Ensure backward compatibility is maintained
  • Document any manual testing steps performed
• Update the documentation for the changes

Documentation Changes

• Run uv run poe doc locally to ensure the documentation pages renders correctly
• Check and fix any broken links (internal or external) in the documentation

When running uv run poe doc, any broken internal documentation links will be reported in the console output like this:

INFO    -  Doc file 'config.md' contains a link 'commands/bump.md#-post_bump_hooks', but the doc 'commands/bump.md' does not contain an anchor '#-post_bump_hooks'.

Expected Behavior

The project's README.md should now verifyably include a Star History chart section near the bottom.

Steps to Test This Pull Request

1. Checkout the branch docs/add-star-history.
2. Open docs/README.md locally or preview the file on GitHub or run uv run poe doc.
3. Scroll down to the bottom of the document (just above the Sponsors section).
4. Verify that the Star History header and the corresponding chart image are visible and render correctly.

Additional Context

[bearomorphism]

LGTM, thanks!