Make admonitions work (more highlighted boxes around PROTIP and TRY IT sections)

[colindean]

Is your feature request related to a problem? Please describe.

It's kinda hard to see the PROTIP and TRY IT sections. They stand out only with the bold text.

Describe the solution you'd like

I'd like for these sections to be highlighted in some way, perhaps with a graybox or colored line and icon.

https://github.com/chdemko/pandoc-latex-admonition should be able to do this but when I tried it, I got build errors.

[colindean]

I was hitting the same problem I've now filed an issue for in chdemko/pandoc-latex-admonition#9