chore(www) Update nested markdown when prettier is upgraded to 1.19.2/1.20.0

[tesseralis]

Summary

PR #21671 switches us to use Prettier's MDX parser. Which mostly works, but it behaves weirdly when pages have nested files, as in the following cases:

• hard wraps prose
• fails without prettier-ignore
• requires Link instead of markdown links
• fails footnotes

The primary issue is that prettier fails when parsing nested markdown in MDX, which will be fixed soon: prettier/prettier#7041

[github-actions]

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