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.

db/migrate/20220710102457_add_display_name_to_tags.rb

@@ -0,0 +1,5 @@
+class AddDisplayNameToTags < ActiveRecord::Migration[6.1]
+  def change
+    add_column :tags, :display_name, :string
+  end
+end

db/migrate/20220714171049_create_tag_follows.rb

@@ -0,0 +1,12 @@
+class CreateTagFollows < ActiveRecord::Migration[6.1]
+  def change
+    create_table :tag_follows do |t|
+      t.belongs_to :tag, null: false, foreign_key: { on_delete: :cascade }
+      t.belongs_to :account, null: false, foreign_key: { on_delete: :cascade }, index: false
+
+      t.timestamps
+    end
+
+    add_index :tag_follows, [:account_id, :tag_id], unique: true
+  end
+end