feat(route): github discussion add category filter

[waynzh]

Involved Issue / 该 PR 相关 Issue

Close #

Example for the Proposed Route(s) / 路由地址示例

/github/discussion/DIYgod/RSSHub/all/Ideas

New RSS Route Checklist / 新 RSS 路由检查表

• New Route / 新的路由
  • Follows Script Standard / 跟随 路由规范
• Anti-bot or rate limit / 反爬/频率限制
  • If yes, do your code reflect this sign? / 如果有, 是否有对应的措施?
• Date and time / 日期和时间
  • Parsed / 可以解析
  • Correct time zone / 时区正确
• New package added / 添加了新的包
• Puppeteer

Note / 说明

[github-actions]

Successfully generated as following:

http://localhost:1200/github/discussion/DIYgod/RSSHub/all/Ideas - Failed ❌

HTTPError: Response code 503 (Service Unavailable)

Error Message:<br/>ConfigNotFoundError: GitHub Discussions RSS is disabled due to the lack of &lt;a href=&quot;https://docs.rsshub.app/deploy/config#route-specific-configurations&quot;&gt;relevant config&lt;/a&gt;
Route: /github/discussion/:user/:repo/:state?/:category?
Full Route: /github/discussion/DIYgod/RSSHub/all/Ideas
Node Version: v22.9.0
Git Hash: 456b5560