Move regex searches to a web worker to stop the browser from hanging
Revert "Merge branch 'countMatches'"

This reverts commit 92df8214f7e9a6fe4535fde35bcd2a9d84f6a91f, reversing
changes made to 21a98a966151f573fa2eeaab7ad433a13c53c794.
Merge branch 'backgroundRegexpSearch'