Add more official plugins

[chrisjsewell]

• https://github.com/markdown-it/markdown-it-container: could be used for Add support for rendering admonitions using "markdown friendly" syntax MyST-Parser#154
• https://github.com/markdown-it/markdown-it-deflist: Add support for defintion lists MyST-Parser#153
• https://github.com/markdown-it/markdown-it-abbr: could be used for substitutions Add substitution syntax(?) MyST-Parser#172?
• https://github.com/markdown-it/markdown-it-sub: e.g. H~2~0
• https://github.com/markdown-it/markdown-it-sup: e.g. 29^th^

(and integrate with myst-parser)
(also amsmath is still to be integrated, see executablebooks/MyST-NB#126 (comment))

[jace]

@miteshashar ported abbr, sub, sup and other plugins for our app that uses Markdown-It-Py. Code here: https://github.com/hasgeek/funnel/tree/main/funnel/utils/markdown/mdit_plugins. We worked independently as we had a timeline to finish in, but we'll happy to contribute them here.

[miteshashar]

I will be happy to be involved, as necessary.

[chrisjsewell]

That would be great thanks

[miteshashar]

@chrisjsewell I saw your response now – a little too long.
I can work on this over the coming few weeks.