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

Conflicts:
- `config/webpack/shared.js`:
  Upstream has changed how Tesseract.js gets included and dropped a dependency.
  The conflict is caused by glitch-soc having different code due to its
  theming system.
  Ported upstream changes.
- `lib/mastodon/version.rb`:
  Upstream refactor/code style change in a place we replaced upstream's
  repo URL with ours.
  Ported upstram changes, keeping our repo URL.
- `yarn.lock`:
  Upstream dropped dependencies, one of which was textually too close to
  a glitch-soc-specific dependency. Not a real conflict.

lib/mastodon/version.rb

@@ -33,16 +33,16 @@ module Mastodon
     end
 
     def repository
-      ENV.fetch('GITHUB_REPOSITORY') { 'glitch-soc/mastodon' }
+      ENV.fetch('GITHUB_REPOSITORY', 'glitch-soc/mastodon')
     end
 
     def source_base_url
-      ENV.fetch('SOURCE_BASE_URL') { "https://github.com/#{repository}" }
+      ENV.fetch('SOURCE_BASE_URL', "https://github.com/#{repository}")
     end
 
     # specify git tag or commit hash here
     def source_tag
-      ENV.fetch('SOURCE_TAG') { nil }
+      ENV.fetch('SOURCE_TAG', nil)
     end
 
     def source_url