[miohtama]

Github already supports Restructured Text (reST) in READMEs, and some other markdown flavours. Do not know about AsciiDoc but looks interesting.

[ygra]

As can be seen here, GitHub renders Asciidoc just fine: https://github.com/asciidoctor/asciidoctor.js

[conaclos]

According to GitHub Docs [1], GitHub supports several markup languages, including Markdown, AsciiDoc, Textile, ReStructuredText, Rdoc, Org, Creole, MediaWiki, and Pod.

[1] https://docs.github.com/en/github/managing-files-in-a-reposi...

[stock_toaster]

Alas, no support[1] for include.

[1]: https://github.com/github/markup/issues/1095