Documentation refactoring

[Bituvo]

Ready for review (and possibly becoming a 5.9 milestone)!

This PR adds these things to the documentation:

• Modern primary and secondary headings
• Capitalized headers
• Slightly less whitespace before primary headers
• Github flavored warnings and information boxes
• Lua code blocks where appropriate
• Tables where appropriate
• Inline code blocks where appropriate
• Removal of extra whitespace in tables ({ min=3, max=5 } -> {min=3, max=5})
• Typo fixes (especially id instead of ID)
• Removed table of contents from /README.md as Github has a builtin one

To do (preferably in a different PR, just putting it out there):

• Use a consistent maximum line width (maybe increasing with each level of bullet points)
• Scour for typos and other mistakes
• Redo protocol.txt

Some people still use the plaintext version of the Lua API, so I tried to maintain readability while still simplifying things.
The original PR for this was #13494, but it was messed up because I forgot to create a new branch.

[appgurueu]

Regarding the table of contents (ToC), the same as for the other PR applies:

I feel like such a table of contents is (1) redundant and (2) probably will eventually be out-of-sync with the document. I think generating a ToC is the job of Markdown renderers.

And as ruben pointed out, "GitHub shows a table of contents in the top left."

[AFCMS]

This is something I really like.

I considered it when making #13439

[Bituvo]

If that wasn't done already, I would have done that in this PR :)

[Bituvo]

Self-review

[rollerozxa]

There's quite a lot of noise in the PR caused by ". " being replaced with ". " in things such as code comments. (as well as translation files which I think shouldn't be touched?)

[Zughy]

@Bituvo rebase needed

[Zughy]

Actually, according to https://irc.minetest.net/minetest-dev/2024-01-15#i_6146082, I don't this PR will make it. If split into smaller PRs and if covering only relevant aspects (see Rollerozxa comment), I guess there won't be big issues though

[Bituvo]

Actually, according to https://irc.minetest.net/minetest-dev/2024-01-15#i_6146082, I don't this PR will make it. If split into smaller PRs and if covering only relevant aspects (see Rollerozxa comment), I guess there won't be big issues though

@Zughy I completely understand. A new PR has been opened, much cleaner and with less noise: #14287