Feature: support markdown alerts (callouts)

[kirasok]

Alerts are blockquotes that are displayed with distinctive colors and icons to indicate the importance of the content

Note

Alerts are currently supported on Github and Obsidian

I think it would be in scope of headlines.nvim to highlight alerts background and replace the heading with icon + title of their respective types

[lukas-reineke]

Yeah sounds good.
Not sure when I'll have time for this though.