docs: add reference to Issue #508 in README for the developer skills cha

[gordonzhaomwrf-a11y]

在 README 中添加指向 Issue #508 的引用，说明该问题涉及 Memanto + mattpocock 开发者技能挑战，方便贡献者了解背景。

Summary by CodeRabbit

• Documentation
  • Updated README with information about developer skills challenge participation and related resources, plus minor formatting improvements for consistency.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 3db0b67a-a877-4521-a088-e5830695223e

📥 Commits

Reviewing files that changed from the base of the PR and between dd38ad3 and c041934.

📒 Files selected for processing (1)

• README.md

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📝 Walkthrough

Walkthrough

The README adds a participation note for the Memanto + mattpocock Developer Skills Challenge with a link to Issue #508, and adjusts markdown table separator formatting in the comparison section for consistency.

Changes

README Documentation Updates

Layer / File(s)	Summary
Challenge participation note and table formatting README.md	Added a bold note indicating participation in the Memanto + mattpocock Developer Skills Challenge with a link to Issue #508. Adjusted markdown table separator row formatting in the comparison table for consistency.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

A dash here, a note there, ✨
🐰 hops through docs with care,
Challenge noted, tables aligned—
README blooms, neatly refined! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a reference to Issue #508 in the README for the developer skills challenge.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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• Create PR with unit tests

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