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

Conflicts:
- `Gemfile.lock`:
  Not a real conflict, just a glitch-soc-only dependency too close to a
  dependency that got updated upstream. Updated as well.
- `app/models/status.rb`:
  Not a real conflict, just a change too close to glitch-soc-changed code
  for optionally showing boosts in public timelines.
  Applied upstream changes.
- `app/views/layouts/application.html.haml`:
  Upstream a new, static CSS file, conflict due to glitch-soc's theming
  system, include the file regardless of the theme.
- `config/initializers/content_security_policy.rb`:
  Upstream dropped 'unsafe-inline' from the 'style-src' directive, but
  both files are very different. Removed 'unsafe-inline' as well.

app/javascript/styles/mastodon/components.scss

@@ -1318,8 +1318,13 @@
 
 .account__avatar {
   @include avatar-radius;
+  display: block;
   position: relative;
 
+  width: 36px;
+  height: 36px;
+  background-size: 36px 36px;
+
   &-inline {
     display: inline-block;
     vertical-align: middle;