Adds anchor block support to List Items

[tomdevisser]

Adds anchor block support to List Items, in it's block.json, and updated the docs accordingly. This couldn't be done before, as the List Item wasn't a child block back then.

Fixes #29838

[ejnwebmaster]

I'm new this, but this seems so close to being complete. Is there a way to bring this to closure? I appreciate the hard work by all, truly.

[github-actions]

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