💥 Role / Directive Refactor

[fwkoch]

markdown-it-myst is a new package to generically parse roles/directives into tokens. It does a nested parse to tokenize args/options/content as well, passing along both the raw role/directive content and the tokenized content.

This package does not define custom role/directive types; those are defined downstream as AST transforms on content made available here.

This package is the first step in addressing #181

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Update

This PR has consolidated the work on markdown-it-myst with myst-parser #193 and myst-roles/directives #206 - it addresses all the refactoring described in #181

[rowanc1]

I think that the only bugs that are left are around the card headers.

It would be great to have tests on the remaining directives, but also want to get this in and out the door! I think there is another pass on validation we need to do, but that can come in next, I don't think we actually loose that much?

[rowanc1]

Some known things:

• Alignment of images is a regression.
• And better validation of width/height.
• figure classes did a bit more on pulling off 'center' and making that the align key.

Anything else?

I think those can easily come in a validation pass.