Enable admonitions #2771
Description
Problem
Admonitions provide a convenient way to highlight a block in a particular way.
GitHub admonitions are documented at https://github.com/orgs/community/discussions/16925, and are used in various other markdown tools.
These seem to be growing in more common usage, and since pulldown-cmark handles it natively now, it shouldn't be too much trouble to support it.
Proposed Solution
After updating to pulldown-cmark 0.13, enable the ENABLE_GFM option. Unfortunately I don't know why this particular feature is grouped under that option, since there are a bunch of other "github flavor" options which are separate. It isn't clear to me why it is organized that way, or if there is risk of it growing more capabilities in the future.
The spec is at: https://github.com/pulldown-cmark/pulldown-cmark/blob/master/pulldown-cmark/specs/blockquotes_tags.txt
Unfortunately the current implementation is hard-coded to a specific set of keywords. There is an open issue for custom tags at pulldown-cmark/pulldown-cmark#919.
This will need to be gated behind a flag, though I think we can roll with it enabled by default in 0.5.
Notes
No response