markup/goldmark: add support for CJK extension

[henry0312]

This commit fixes #10472.

To make this PR function more accurately, merging yuin/goldmark#409 is needed.

[CLAassistant]

All committers have signed the CLA.

[henry0312]

goldmark v1.5.6 has been released (cf. #11365).
The features implemented in the pull request work fine, and it is ready for merging.

[bep]

Thanks, this looks good.

I do, however, notice that there are 2 additional options on this extension:

https://github.com/yuin/goldmark#cjk-extension

I assume someone will ask for these at some point, so I think we might as well make the new config option a map, e.g.:

[markup]
[markup.goldmark]
[markup.goldmark.extensions.CJK]
enable=false
eastAsianLineBreaks=false
escapedSpace=false

[henry0312]

I updated and added two options.
At first, I anticipated that those who want to enable the CJK option would also want to enable the eastAsianLineBreaks and escapedSpace features simultaneously.
However, I now believe that making those two options certainly provides more flexibility.

[bep]

Thanks, I will merge once the tests go green.

A side note for future reference; the docs.yaml file is autogenerated (I do it before a new release) so any manual edits will be overwritten (which is why it doesn't matter much ...).

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