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

Conflicts:
	Dockerfile
	app/javascript/packs/common.js
	config/webpack/loaders/sass.js
	config/webpack/shared.js
	db/schema.rb
	package.json
	yarn.lock

A lot of the conflicts come from updating webpack.

Even though upstream deleted app/javascript/packs/common.js, I kept
glitch-soc's version as it unifies JS/CSS packs behavior across flavours.

Ported glitch changes to webpack 4.x

app/serializers/initial_state_serializer.rb

@@ -19,6 +19,7 @@ class InitialStateSerializer < ActiveModel::Serializer
       domain: Rails.configuration.x.local_domain,
       admin: object.admin&.id&.to_s,
       search_enabled: Chewy.enabled?,
+      version: Mastodon::Version.to_s,
       invites_enabled: Setting.min_invite_role == 'user',
     }