Add Missing Content Script e2e Test

[benjamin-chavez]

Add a single URL that the extension's host permissions are blocked from accessing. Something self-hosted just for testing. Then add test cases to ensure that the behavior of the searching and matching logic does not change in any way.

There was a previous bug (now fixed) that was related to this where the first match on a tab was not being updated to have the focus-highlight color while navigating through matches.