#23 Enhancement: Warning/note/info blocks

A useful block type for documentation would be callout blocks for different kinds of info, including warnings, additional information, special notes, maybe others. No direct HTML equivalent except perhaps some document structure markers. Typically rendered as a bordered box with a large icon in the left margin, like :information_source: or :warning:.

Syntax could look something like:

(i) Info box

(!) Warning box

See Github https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#alerts