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

- `.env.production.sample`:
  Our sample config file is very different from upstream since it is much more
  complete. Upstream added documentation for a few env variables.
  Copied the new variables/documentation from upstream.
- `app/lib/feed_manager.rb`:
  Upstream added a timeline type (hashtags), while glitch-soc already had an
  extra one (direct messages). Not really a conflict but textually close
  changes.
  Ported upstream's changes.
- `app/models/custom_emoji.rb`:
  Upstream upped the custom emoji size limit, while glitch-soc had configurable
  limits.
  Upped the default limits accordingly.
- `streaming/index.js`:
  Upstream reworked how hastags were normalized. Minor conflict due to
  glitch-soc's handling of instance-local posts.
  Ported upstream's changes.

app/serializers/activitypub/hashtag_serializer.rb

@@ -10,11 +10,11 @@ class ActivityPub::HashtagSerializer < ActivityPub::Serializer
   end
 
   def name
-    "##{object.name}"
+    "##{object.display_name}"
   end
 
   def href
-    if object.class.name == 'FeaturedTag'
+    if object.instance_of?(FeaturedTag)
       short_account_tag_url(object.account, object.tag)
     else
       tag_url(object)