Regex for @see linking of hooks recognize hook names contain variables

[coffee2code]

For example, in the description for ​wp_transition_comment_status() there is a reference to a hook that looks like this:

{@see 'comment_$new_status_$comment->comment_type'}

However, it fails to be recognized as a hook due to the presence of & and ; (that were introduced by the encoding of > to >) and the - that the regex in link_internal_element() doesn't expect. Thus, the resulting link is the fallback assumption that the reference is to a function.

(Note that as of this posting there is an unrelated bug that also affects the aforemention link, which will be addressed in #2881.)

[coffee2code]

In 5578:

developer.wordpress.org: Change regex for @see linking of hooks to recognize characters and HTML entities that may be present in hook names.

This is valid {@see 'comment_$new_status_$comment->comment_type'} but failed to be recognized as a hook due to the presence of & and ; (from the encoded value of >) and the -.

Example: ​https://developer.wordpress.org/reference/functions/wp_transition_comment_status/

Fixes #2880.