Table of Contents (TOC) can be folded

[dunizb]

The generated Table of Contents (TOC) can be folded just fine

[pbreheny]

Just wanted to bump/second this issue. A very common situation for me is that I want to display the TOC so that I can navigate to a new section, but it takes up too much of the screen, so I want to hide it, and constantly go back and forth. Would be very convenient if there was a collapsible TOC, something like this.

P.S. @simov, great work on this wonderful software.