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

config/webpack/loaders/sass.js

@@ -1,15 +1,27 @@
-const ExtractTextPlugin = require('extract-text-webpack-plugin');
+const MiniCssExtractPlugin = require('mini-css-extract-plugin');
 const { env } = require('../configuration.js');
 
 module.exports = {
-  test: /\.(scss|sass|css)$/i,
-  use: ExtractTextPlugin.extract({
-    fallback: 'style-loader',
-    use: [
-      { loader: 'css-loader', options: { minimize: env.NODE_ENV === 'production' } },
-      { loader: 'postcss-loader', options: { sourceMap: true } },
-      'resolve-url-loader',
-      { loader: 'sass-loader', options: { includePaths: ['app/javascript'] } },
-    ],
-  }),
+  test: /\.s?css$/i,
+  use: [
+    MiniCssExtractPlugin.loader,
+    {
+      loader: 'css-loader',
+      options: {
+        minimize: env.NODE_ENV === 'production',
+      },
+    },
+    {
+      loader: 'postcss-loader',
+      options: {
+        sourceMap: true,
+      },
+    },
+    {
+      loader: 'sass-loader',
+      options: {
+        includePaths: ['app/javascript'],
+      },
+    },
+  ],
 };