https://github.github.com/gfm/

https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax
https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/quickstart-for-writing-on-github

tips
https://github.blog/developer-skills/github/github-protips-tips-tricks-hacks-and-secrets-from-lee-reilly/
https://github.blog/developer-skills/github/github-protips-tips-tricks-hacks-and-secrets-from-vitor-monteiro