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

Conflicts:
- `README.md`:
  Minor upstream change, our README is completely different.
  Kept ours.
- `lib/tasks/assets.rake`:
  glitch-soc has extra code to deal with its theming system,
  upstream changed a line that exists in glitch-soc.
  Applied upstream changes.

lib/mastodon/premailer_webpack_strategy.rb

@@ -13,7 +13,7 @@ module PremailerWebpackStrategy
             HTTP.get(url).to_s
           else
             url = url[1..-1] if url.start_with?('/')
-            File.read(Rails.root.join('public', url))
+            File.read(Rails.public_path.join(url))
           end
 
     css.gsub(/url\(\//, "url(#{asset_host}/")

lib/mastodon/statuses_cli.rb

@@ -93,7 +93,7 @@ module Mastodon
         c.table_name = 'statuses_to_be_deleted'
       end
 
-      Object.const_set('StatusToBeDeleted', klass)
+      Object.const_set(:StatusToBeDeleted, klass)
 
       scope     = StatusToBeDeleted
       processed = 0
@@ -175,7 +175,7 @@ module Mastodon
         c.table_name = 'conversations_to_be_deleted'
       end
 
-      Object.const_set('ConversationsToBeDeleted', klass)
+      Object.const_set(:ConversationsToBeDeleted, klass)
 
       scope     = ConversationsToBeDeleted
       processed = 0