Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- app/javascript/mastodon/features/compose/components/compose_form.js
  Upstream cleaned up a bit, including on lines in which
  we replaced the hardcoded 500 character limit with a maxChar
  constant. Applied the changes while keeping maxChar instead of 500.
- app/javascript/packs/public.js
  Moved upstream's new animated avatar hover handling in
  app/javascript/core/public.js
- app/javascript/styles/fonts/montserrat.scss
  Upstream fixed local font name, applied those changes.
- app/javascript/styles/fonts/roboto.scss
  Upstream fixed local font name, applied those changes.
- lib/mastodon/version.rb
  Upstream made repo URL configurable, did the same, but
  default to glitch-soc

lib/mastodon/version.rb

@@ -37,11 +37,11 @@ module Mastodon
     end
 
     def repository
-      'glitch-soc/mastodon'
+      ENV.fetch('GITHUB_REPOSITORY') { 'glitch-soc/mastodon' }
     end
 
     def source_base_url
-      "https://github.com/#{repository}"
+      ENV.fetch('SOURCE_BASE_URL') { "https://github.com/#{repository}" }
     end
 
     # specify git tag or commit hash here