docs: add heads up for Prettier users

[tats-u]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

#9318

Test Plan

Test links

Deploy preview: https://deploy-preview-_____--docusaurus-2.netlify.app/

Related issues/PRs

Fix #9318

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 72	🟢 98	🟢 100	🟢 100	🟠 89	Report
/docs/installation	🟠 66	🟢 98	🟢 100	🟢 100	🟠 89	Report
/docs/category/getting-started	🟠 76	🟢 100	🟢 100	🟢 90	🟠 89	Report
/blog	🟠 75	🟢 100	🟢 100	🟢 90	🟠 89	Report
/blog/preparing-your-site-for-docusaurus-v3	🟠 63	🟢 97	🟢 100	🟢 100	🟠 89	Report
/blog/tags/release	🟠 74	🟢 100	🟢 100	🟠 80	🟠 89	Report
/blog/tags	🟠 74	🟢 100	🟢 100	🟢 90	🟠 89	Report

[tats-u]

Changed the version of MDX because of #9451

[Josh-Cena]

I have just been bitten by this recently. I think this helps users more than it harms us, and the wording is currently good enough, so I'm going to merge it. Thank you!

[tats-u]

It looks like the content of this PR has not been merged into the 3.1.0 document.