Feature idea: admonitions

[giltho]

I find admonitions to be particularly helpful, particularly for warnings and danger. See for instance this example in the documentation of React where a "Pitfall" admonition warns of common errors.

Something like:

{note ...}
{tip ...}
{warn ...}
{important ...}
{caution ...}

I chose these specific kinds based on what Github has, but it could be others.

[yawaramin]

Can we use similar styling for maybe warn/caution and @raise? Currently @raise rendering is very bare-bones, I feel like it would be better styled as a sort of admonition.

Eg