Support admonition markdown extension syntax

[mschoettle]

Is your feature request related to a problem?

Hi @aepfli. I came across your rule through the discussion on one of the markdownlint repos. Thanks for this rule!

I started trying it out and there is one case where this rule complains that would be nice if it supported it.

We use mkdocs-material (https://squidfunk.github.io/mkdocs-material/) and make use of the admonition extension (see https://squidfunk.github.io/mkdocs-material/reference/admonitions/).

Unfortunately all lines with !!! ... and ??? ... (e.g., !!! note) cause a max-one-sentence-per-line violation.

Describe the solution you'd like

It would be great if this admonition syntax could be excluded without requiring to specifically add disable comments on the preceding line.

Describe alternatives you've considered

See above.

Additional context

n/a

[aepfli]

Hey, first of all, thank you for the issue. I am happy that my code helps some people out there.

The solution I propose in #52 is merely a bandaid and a hack around the problem. But till I come up with a better solution, I think it is feasible with little configuration effort.

I'll think about a better approach, but please let me know if this helps you and is sufficient for the time being.

all the best
simon

[mschoettle]

Thanks Simon for the quick response and fix. This workaround would help for the time being.