Consider adding ToC for larger documentation entries

[szuend]

I was just browsing the Torque user manual and thought a table of contents or something similar would be nice for larger articles. Especially for articles like the torque user manual, where readers might only be interested in one specific section.

[mathiasbynens]

I started looking into this, and then hit https://github.com/Oktavilla/markdown-it-table-of-contents/issues/38. Luckily, we can work around it, but it feels dirty.

WIP branch: https://github.com/v8/v8.dev/compare/toc?expand=1 (We still need to tweak the output HTML and add some styling.)

[camillobruni]

Declaring bug bankruptcy after 4 years of inactivity.