Feature Request: Collapse/Expand sections in API reference

**DocFX Version Used**: 2.23

**Template used**: `default`

When navigating to a namespace (for example: https://tzachshabtay.github.io/MonoAGS/api/AGS.API.html), I would like to have `Classes`, `Structs`, `Interfaces`, `Enums` and whatever other sections might be there as collapsible/expandable sections.

Similarly, when navigating to an interface/class/struct (for example: https://tzachshabtay.github.io/MonoAGS/api/AGS.API.IAnimation.html), I would like to have `Properties`, `Methods` and whatever other sections might be there as collapsible/expandable sections.

Thank you.

Start by examining the default template's generated API reference pages, using the linked namespace and interface examples as entry points. Verify how namespace sections and type-member sections are rendered, then confirm that both kinds of pages can collapse and expand their sections consistently.

Written by the indexing model from the issue text.