Currently, the getting started text fails WCAG standards for color contrast by a lot. Especially on the part overlapping with the elephant graphic which is nearly unreadable even for users with 20|20 vision. This change doesn't fix the elephant overlap but at least makes the text meet AAA WCAG Small Text color contrast standards, making it easier to read.

fix up spoilers

Federate spoiler_text using warning attribute on <content /> instead of a <category term="spoiler" />
Clean up schema file from accidental development migrations

in the background instead. Should fix delay where blocked person
can interact with blocker for a short time before background job
gets processed

Fix `invisible` CSS class

affected, replaced onClick handler with onMouseUp/Down to detect text
selection not trigger onClick handler then

background as well since it's a computationally expensive

now return empty hash instead of throwing a 404 error. When following,
merge into timeline will filter statuses

Fix #365, 1/2 of #408 - replace rails_autolink with URI.regexp, run link_hashtags on simplified_format