Support python-markdown admonition extension

[cas--]

I noticed when converting some Material MkDocs pages with md2cf that admonitions were not converted:

!!! cite "A great man once said ..."

It seems that mistune has it's own admonition directive but would it be possible to add support for python-markdown admonition extension as a plugin?

Material MkDocs has a list of supported types with a fallback to note if unrecognised.

[cas--]

Closing since this as just read that this is Mistune Flavored Markdown (MFM) so not likely to add this if already has own admonition directive

[lepture]

@cas-- you can actually create a plugin yourself.