Refactor markdown files

[Bituvo]

Ready for review

This is a better version of #13503, but without so much noise. Only markdown files (and worlds_here.txt) were changed.

This PR adds these things to the documentation:

• Modern primary and secondary headings
• Capitalized headers
• Slightly less whitespace before primary headers (three lines)
• 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
• And more

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.

[appgurueu]

First, an observation: This PR does not require a core dev to review it. I suggest the @minetest/docs team (or anyone trustworthy, really) be allowed to review this (and have their approval count).

Github flavored warnings and information boxes

I recently (regrettably) pushed such a change; I'll have to fix it (or you could fix it here too, if you want). This seems to not render correctly on https://api.minetest.net. I think we want to stick to plain Markdown, for now.

[Bituvo]

Github flavored warnings and information boxes

I recently (regrettably) pushed such a change; I'll have to fix it (or you could fix it here too, if you want). This seems to not render correctly on https://api.minetest.net. I think we want to stick to plain Markdown, for now.

That website uses MkDocs, which supports extensions. There are already a few extensions enabled here and after some searching I found https://pypi.org/project/markdown-gfm-admonition/, which enables Github admonition boxes. I personally haven't tried testing this extension (I am too busy), but it looks promising, to whoever may be able to try.

[Bituvo]

@Zughy Whose opinion should I get on this?

[Zughy]

It was about the GH info boxes but I guess it's been solved

[Bituvo]

@sfan5 Thank you so much for digging through this pull. I would never have the time or energy to do it myself, so help is always appreciated. I hope you agree with my changes.

[sfan5]

Should be fine, can you merge/rebase the last tiny change?

[Bituvo]

Merge conflicts have been resolved.