Add a table of contents element

[cswimr]

We need a table of contents element, especially for longer pages. I'm not sure where we can put it in the current site design aside from the top of the page. Potentially a sidebar?
See TableOfContents for more info on Hugo's ToC generation.

[smallketchup82]

id like to avoid having this be in the page content. but at the same time it'd look weird if it was on top of the pitch black background.

my thoughts is we could put a button in the topbar that when clicked, shows the TOC. similar to the "On this page" that fmhy.net has: https://fmhy.net/videopiracyguide