Statically generate ToC and Sections

[lord]

We're hosting static content, so we should be able to create the table of contents and <section>s before sending it to the user. This probably also involves removing Tocify.

Also #551 mentions preserving italics, which is a good idea.

[seweil]

Yes, building the TOC DOM dynamically appears to take about 40% of page load time.
Another possible approach is to save the TOC from the browser at 'build' time.

[PreciselyAlyss]

Going through the V2 feature branch, it seems that it only headers are only identified if they are used in the index page and not if they are within the included files. Is there a good way to be able to read the headers out of included files or is this a limitation of that current feature implementation?

[lord]

Added in the dev branch! Let me know if anybody runs into issues with the new code.

@bc-AlyssNoland thanks for the catch, this should be fixed in the latest toc generation implementation!

[seweil]

@lord - If we want to try static TOC, would you recommend that we apply #701 to the release branch, or run with the dev branch? (E.g. can you comment on completeness and stability?)

[lord]

@seweil I'd try out the dev branch! There may be a few remaining bugs with it, but applying #701 to the release branch would result in the same bugs or maybe even more.