Quoting now also includes the spoiler and code tags.
Fix quoting on Firefox.
Don't leave an extra `>` when quoting.
Fix handling <br>s when quoting selection in QR

The previous code caused, among others, merging of two-line selections
into one line.
Fix Remove Spoilers stripping tags.
Fix quoting inside of spoiler/code tag when common ancestor is not text node.
Make [spoiler] quoting compatible with Remove Spoilers.
Remove (embed) links from quotes.
README.md: Uninstalling and native extension.
Build web page.
Don't add quote markers inside [code] tags.
Restore titled links when quoting.
Remove positive tabindex.
Better cleaning of beginnings of links.
Fix text content of Linkify ranges, add test.
Need to account for subdomains now that regexp is being used to clean start of link.
Fix nondetection of plain domain names when followed by space.
Only need regexp.test here.
Release 4chan X v1.9.15.0.