Add auto generated HTML pages

[paypur]

I think I'm pretty close to being done, so here's what I have. There's definitely even more that can be done, like the tooltips we talked about, but that will have to be for later.

Preview: https://paypur.github.io/docs/books/1.20/
Tinkers' PR: SlimeKnights/TinkersConstruct#5456
Mantle PR: SlimeKnights/Mantle#231

Notes

• PageContent's should override toHTML
• The auto-generated HTML is not very readable but I'm not sure if you care because you shouldn't manually edit it
• CSS is written assuming scale = 2, but this should be easy to change
• The old images are still there for comparing
• All images have been index with 8-bit color (if possible) then losslessly compressed
• Exporting has been split off into /mantle book export_html
• The book "chapters" feel kinda redundant now that we can just link to a specific page on an image
• Non Tinker's books might need to be updated to work with this

Still TODOs

• Fix ContentListings overflowing
• Compress the .png's
• Remove unnecessary HTML?? (like newlines)
• Add back the previous page layout for old versions
• Fix issues on mobile
• Rebase before we merge

[KnightMiner]

Something important to note: I don't want to replace the existing picture based books with HTML ones. I would rather have both. The reason is the image ones are way more likely to be stable on the chance the HTML updater breaks in the future, and are way more likely to be accurate across devices.

You will likely want a separate home page for HTML books vs image books, with links between the two as relevant.

[paypur]

Would it be better for the HTML books to be the primary, and the image books to be the fallback in case of any issues?

[KnightMiner]

Neither is really primary or fallback. They are just different pages. The book index can link them both:

Icon
Title
HTML / Images

Key thing is I want to have both. I find images works very nicely on mobile notably.

[paypur]

Everything is all merged again. You definitely need to squash this PR, I've updated the images like 10 times and it would bloat the git repo otherwise. One other important thing is I've losslessly compressed ALL images since it wasn't too hard. I can revert the changes to images unrelated to this PR if you want.

[KnightMiner]

Yeah, probably best to ensure you are not modifying any images unrelated to this PR.

We can do lossless compression later.