Converted the readme to markdown for accessibility

[eigencrow]

Plain text files are difficult to skim with a screenreader, because they contain no semantic information. A readme is the type of file one often needs to skim, to find platform-specific build instructions, website links, release notes, etc. Because markdown can be rendered as semantic HTML, it is inherently more accessible to screenreaders, and possibly more user friendly to those less familiar with GitHub. I manually converted the whole repo readme to markdown, flattening indented lines according to the style I know and use. The biggest changes are turning the section titles into headings, and making the directory structure into a table.

I used minimal emphasis, partly to avoid the LLM flavor, mostly because it was plain text to begin with and I didn't want to unintentionally change any meanings. I only emphasized text where a previously indented line seemed to be doing so.

I didn't format the release notes at all, beyond giving each version a heading at level 3, and Linus's library bugfixes/releases at level 4. This is for the reasons already mentioned, and also because it's a lot of text to format by hand, although I want to for completionist reasons. I do think the release notes would be better off in a separate document, linked to by the readme, but that's an issue for another issue.

[dstelzer]

This all looks good to me! The one change I'd request is adding a line to the changelog mentioning converting the README to Markdown.

[eigencrow]

Done! I classified it as "Documentation" as I wasn't sure what else it should be. Lemme know if that's wrong. :7

[dstelzer]

Looks good to me!