Previously this inline-tag-def was returning the `doc` which is rendered
to the output as `[Object Object]` - obviously not what is intended.
Now it returns `''` which effectively strips the tag handler from the
rendered output.
PR Close#37132
This commit adds a new preprocessor to use `${@searchKeywords}`, allowing
the docs to use a list of custom search phrases that will be
prioritized over the keywords found in the content.
Closes#35449
PR Close#35539