Draft: Reformat modulesets-stable using HTML tidy

Following our discussion in #65 (closed), this is my proposal on reformatting the module sets. Except for some one-time reformatting of the comments that I did manually, everything else is handed off to tidy (https://github.com/htacg/tidy-html5). Taste is debatable and it's surely not perfect (if there even is such a thing), but I think it is a helpful improvement.

This MR is in draft mode as I still need to run some builds to make sure I haven't messed something up by accident. It also only covers the stable module set, I prefer to do this gradually instead of everything at once.