Add reference to the parent tag of the `contentSeparator` tag in its description

Hi! 👋

In order to make it easier to identify that the contentSeparator tag has the content tag as its parent tag in the documentation website, and to be consistent with the other tags, I would like to suggest that this information be added explicitly to the description:

highlight/src/highlight.ts

Lines 566 to 567 in 88ff939

    
           /// A prose separator (such as a horizontal rule). 
        
           contentSeparator: t(content),

The first alternative could be to change A prose separator to A prose [content](#highlight.tags.content) separator, adding the respective link to the content tag.

The second alternative could be to add Subtag of [content](#highlight.tags.content). to the description, similar to what is done for the paren tag, for example.

Let me know your thoughts and if I can open a PR. Thanks!

Good idea. Done in attached patch.

	/// A prose separator (such as a horizontal rule).
	contentSeparator: t(content),