docs: Suggest remark-cjk-friendly in migration guide

[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

It requires a lot of effort to ensure to replace all * and ** not recognized as emphasis markers by CommonMark/MDXv2+ with <em> and <strong> in large CJK documents. I think they cannot be found by a simple regex. It is much easier to depend on remark-cjk-friendly remark plugin for CJK documents.

Test Plan

Check the changed page and confirm it looks great

Test links

Deploy preview: https://deploy-preview-10892--docusaurus-2.netlify.app/docs/migration/v3/#emphasis-starting-or-ending-with-a-space-or-a-punctuation

Related issues/PRs

• docs: add admonition for incompatibility with * and ** in Chinese and Japanese in MDX v2+ #9692
• docs: backport #9471, #9692, and #9695 changes in v3.1.1 docs #9804
• Emphasis with CJK punctuation commonmark/commonmark-spec#650

[netlify]

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🔴 38	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🔴 46	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 72	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 54	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🟠 66	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 62	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 73	🟢 100	🟢 100	🟠 86	Report

[slorber]

thanks