fix(theme): support details/summary in CommonMark + add md dogfood test cases

[slorber]

Motivation

Having similar tests for md/mdx modes ensure we offer a consistent experience to our users.

Currently, those tests show it's not the case, see problems reported here: #9092

Also add better tests for html comments support, cf edge case bug reported here: #9084

This PR is also a mini fix adding support for summary/details in CommonMark mode, see #9092 (comment)

Test Plan

preview

Test links

https://deploy-preview-9093--docusaurus-2.netlify.app/tests/pages/markdown-tests-md

https://deploy-preview-9093--docusaurus-2.netlify.app/tests/pages/markdown-tests-mdx

Related issues/PRs

[netlify]

✅ [V2]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 80	🟢 97	🟢 92	🟢 100	🟠 89	Report
/docs/installation	🟠 74	🟢 100	🟢 92	🟢 100	🟠 89	Report

[github-actions]

Size Change: 0 B

Total Size: 1.1 MB

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	117 kB
website/build/assets/css/styles.********.css	113 kB
website/build/assets/js/main.********.js	828 kB
website/build/index.html	41 kB

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