Merge commit 'b85c387c5c0527b0ad31c27031a09d361826c5fc' into glitch-soc/merge-upstream

Conflicts:
- `config/initializers/content_security_policy.rb`:
  Kept our version, it was not affected by upstream's bug.

lib/mastodon/premailer_webpack_strategy.rb

@@ -16,7 +16,7 @@ module PremailerWebpackStrategy
             Rails.public_path.join(url).read
           end
 
-    css.gsub(/url\(\//, "url(#{asset_host}/")
+    css.gsub(%r{url\(/}, "url(#{asset_host}/")
   end
 
   module_function :load