Docs: 添加插件 metadata 缺失的 docstring

[yanyongyu]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.77%. Comparing base (6689ffb) to head (f03a2fe).
⚠️ Report is 304 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3583   +/-   ##
=======================================
  Coverage   93.76%   93.77%           
=======================================
  Files          48       48           
  Lines        4317     4318    +1     
=======================================
+ Hits         4048     4049    +1     
  Misses        269      269           

Flag	Coverage Δ
unittests	93.77% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

🚀 Deployed to https://deploy-preview-3583--nonebot2.netlify.app