Support CJK Friendly Emphasis extension

[tats-u]

CommonMark's emphasis has a specification bug that is incompatible with Chinese and Japanese.

**この文は太字になりません。**この文のせいで。

This sentence will not be bolded. It is due to this sentence.

↓Wrong

↓It should be

https://github.com/tats-u/markdown-cjk-friendly

This extension significantly improves compatibility with Chinese and Japanese. ** in all the above examples will be properly recognized as <strong> thanks to this extension.

Supported (opt-out):

• VitePress
• GitLab (via Comrak)

Supported (opt-in):

• Comrak / commonmarker

remark plugin usage: https://github.com/tats-u/markdown-cjk-friendly/network/dependents
(markdown-it plugin usage: https://github.com/tats-u/markdown-cjk-friendly/network/dependents?package_id=UGFja2FnZS01NzMwMzc4ODU5)

Playground: https://tats-u.github.io/markdown-cjk-friendly/

Blocked by #860