Implement collapsable navigation menus like Wikipedia on moblie

The Python documentation table of contents is massive. It's unwieldy on a mobile device. A lot of that comes from itemising all the changelogs going back to 3.0 release. In and of itself, that's fine, but it takes a lot of scrolling to find anything. The indentation also isn't terribly clear to identify what is a subheading of what. Highly nested headings exacerbates this.

Collapsable TOC headings, used on sites like Wikipedia, would help tremendously with this. That way, mobile users could see a cleaner layout resembling the desktop TOC display, then be able to drill down into whatever topic they're looking for.

先檢查主題的目錄標記和行動版導覽樣式，然後將目前的巢狀版面配置與 Wikipedia 的可摺疊導覽進行比較。定義標題在行動裝置上應如何展開和摺疊，包括 changelog 區段，並在行動尺寸的文件建置中驗證結果。