Use node-css-loader 5.x and node-postcss 8.x

debian/control

@@ -370,7 +370,7 @@ Depends: ${shlibs:Depends}, ${misc:Depends},
  node-compression-webpack-plugin (>= 3.0.1~),
  node-copy-webpack-plugin (>= 5.0~),
  node-core-js (>= 3.2.1~),
- node-css-loader (>= 2.1.1~),
+ node-css-loader (>= 5.0~),
 # node-d3 includes d3-sankey
  node-d3 (>= 5.16~),
  node-d3-scale (>= 1.0.7~),

debian/patches/0740-use-packaged-modules.patch

@@ -130,7 +130,7 @@ Use debian packaged node modules when available
      "diff": "^3.4.0",
      "document-register-element": "1.14.3",
      "dompurify": "^2.0.11",
-@@ -85,81 +62,46 @@
+@@ -85,81 +62,47 @@
      "editorconfig": "^0.15.3",
      "emoji-regex": "^7.0.3",
      "emoji-unicode-version": "^0.2.1",
@@ -175,6 +175,7 @@ Use debian packaged node modules when available
 -    "prismjs": "^1.21.0",
 -    "prosemirror-markdown": "^1.3.0",
 -    "prosemirror-model": "^1.6.4",
++    "postcss": "8.2.1",
      "raphael": "^2.2.7",
 -    "raw-loader": "^4.0.0",
      "select2": "3.5.2-browserify",