Discuss alternatives to `mdbook-alerts` for callout preprocessors

[mkatychev]

mdbook-alerts seems "good enough" for both the web and Github display, but IMO this is worth bringing up so that everyone can discuss

Originally posted by @vados-cosmonic in #218 (comment)

mdbook-admonish is one alternative to consider for this role:

Pros:

• In use by popular projects such as Tree-sitter
• Uses material design (somewhat subjective but it styling feels clearer)
• handles console outputs as their own element
• does not need workarounds to play nice with mdbook-linkcheck

Cons:

• Does not support > quote blocks Compatibility with GitHub and Pandoc tommilligan/mdbook-admonish#72
• non zero amount of effort to move over to an alternative