Feature Request: Support for Table of Contents Flexmark Extension

[stelcodes]

Hi there! I'm a big fan of Cybermonday, I'm using it in a static site generator I'm working on.

I'm wondering if you'd be open to including support for the Table of Contents Flexmark Extension. Basically you just add a line of [TOC] or [TOC levels=1-3] and you get a table of contents which is just a tree of nested ul elements with links to the heading anchors.

I got excited and actually implemented this today, and from what I can tell it works great! Are you interested in adding this extension/feature? I know you want to keep some parity with the CLJS side. I don't have any code for that atm.

[kiranshila]

Thanks for the PR, Stel! I've been following your static site generator, which looks so cool! I'll take a look at your PR.