In order to add support for the SELECT and TABLE tags in the HTML Processor, it
needs to implement the HTML algorithm named "reset the insertion mode
appropriately".
This patch implements that algorithm to unblock the additional tag support. The
algorithm resets the parsing mode after specific state changes in complicated
situations where alternative rules are in effect (such as rules governing how
the parser handles tags found within a TABLE element).
Developed in https://github.com/WordPress/wordpress-develop/pull/6020
Discussed in https://core.trac.wordpress.org/ticket/61549
Props dmsnell, jonsurrell.
Fixes#61549.
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