Add site icons linking to all the artist's sites in the fetch source
data box.
Some artist entries have a large number of URLs. Various heuristics are
applied to try to present the most useful URLs first. Dead URLs and
redundant URLs (Pixiv stacc and Twitter intent URLs) are filtered out.
Remaining URLs are sorted first by site (to put sites like Pixiv and
Twitter first), then by URL (to break ties when an artist has multiple
accounts on the same site).
Some sites have shitty hard-to-read icons. It can't be helped. The icons
are the official favicons of each site.
* Add Discord, Twitter, and Github links to site footer.
* Remove "Desktop mode" and "Keyboard shortcuts" links from footer.
Users can use the desktop site option in their browser to switch
between desktop and mobile mode.
* Remove git hash from footer. Users can hover over the Github logo to
see the hash instead.
This was used to discourage crawlers from crawling certain pages we
didn't want them to crawl, primarily post searches.
Remove because there are better ways to control crawling. Some of these
links weren't even visible to crawlers anyway. This lets us be
consistent about only applying rel="nofollow" to external links.
