docs: Add missing API ref docs for Docusaurus Faster options

[slorber]

Motivation

Those Docusaurus Faster options are ready to release so let's write a bit more docs since I didn't while iterating.

Test Plan

https://deploy-preview-10630--docusaurus-2.netlify.app/docs/api/docusaurus-config#future

[netlify]

✅ [V2]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🟠 57	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🟠 57	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 74	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 48	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 64	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 75	🟢 100	🟢 100	🟠 86	Report