chore(astToPlainText): processor improvements

[rafegoldberg]

📖 PR App

🧰 Changes

Magic HTML blocks were being entirely skipped when serializing to plain text.

• [x] Reparse HTML blocks instead of serializing to a blank string.
• [x] Fix multi-child callout sub-node serialization.
• [x] Nix the stripTags option; internalized in the astToPlainText processor. (Reverts #914.)
• [x] Add various unit tests for variables, glossary terms, custom HTML blocks, complex callouts, and style tags.

🧬 QA & Testing

Pull down this branch and try running the following snippet. If the HTML block serializes to plain text nicely (instead of giving back a blank string) this worked! :tada:

const docBody = '[block:html]{ "html": "<p>Lorem <b>ipsum</b> dolor sit amet, consectetur adipiscing elit.</p>" }[/block]\n\n> 👍 title\n> complex|multi\n> ---|---\n> child|body';

const output = rdmd.astToPlainText(rdmd.hast(docBody));

Now give the astToPlainText() unit tests a whirl. If everything comes up green, we're good! 🤘

npx jest --watch -- astToPlainText.test.js

[rafegoldberg]

This PR was released!

🚀 Changes included in v6.87.0