Show the table of contents (TOC) in narrow windows

[colbygogan]

Currently when the viewport is resized to a smaller width, the TOC will disappear. It would be helpful to still be able to see the TOC when the viewport is shrunk and/or implement a toggle to show the TOC - similar to the image attached.

[mbostock]

Yes, I’d like this. VitePress does this well by inserting a position-fixed header and then using a popover for the contents.