Render GitHub alers with color and icon as GitHub renders

[lamyergeier]

Command

File="$(basename *.markdown .markdown)"
OutputP="Output/${File}.gen.html"
mkdir -p Output
pandoc "${File}.markdown" -f commonmark_x \
-o "${OutputP}"

I want to render (with icon and color)

> [!NOTE]
> Useful information that users should know, even when skimming content.

> [!TIP]
> Helpful advice for doing things better or more easily.

> [!IMPORTANT]
> Key information users need to know to achieve their goal.

> [!WARNING]
> Urgent info that needs immediate user attention to avoid problems.

> [!CAUTION]
> Advises about risks or negative outcomes of certain actions.

as GitHub does as follows

[jgm]

For HTML output you can do that with some simple CSS.

[jgm]

See related #9475