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/javascript/styles/mastodon/components.scss

@@ -1478,6 +1478,7 @@ a.account__display-name {
   display: flex;
   align-items: center;
   justify-content: center;
+  flex-direction: column;
 
   .image-loader__preview-canvas {
     max-width: $media-modal-media-max-width;
@@ -1486,8 +1487,8 @@ a.account__display-name {
     object-fit: contain;
   }
 
-  &.image-loader--loading .image-loader__preview-canvas {
-    filter: blur(2px);
+  .loading-bar {
+    position: relative;
   }
 
   &.image-loader--amorphous .image-loader__preview-canvas {