Upgrade front end dependencies

Mostly in order to get rid of deprecated deps, and upgrade vulnerable ones.

  - Upgrade webpack from 3.x to 4.x
  - Moved babel package to main repo
  - Replaced deprecated extract-text-webpack-plugin with extract-text-webpack-plugin
  - Replaced deprecated babel-minify-webpack-plugin with terser-webpack-plugin
  - Replaced deprecated node-sass with (dart) sass package
  - Replaced deprecated sass-lint with stylelint (the rules might be a bit different

Related to #1531: trivy doesn't raise any more issue

2 files changed, 15 insertions, 17 deletions

diff --git a/.dev/.sasslintrc b/.dev/.sasslintrc
deleted file mode 100644
index 47c3145d..00000000
--- a/.dev/.sasslintrc
+++ /dev/null
@@ -1,17 +0,0 @@
-options:
-  max-warnings: 0
-rules:
-  property-sort-order:
-    - 0
-# Sort order rule does not work with CSS variables: https://github.com/sasstools/sass-lint/issues/1161
-#    - 1
-#    -
-#      order: 'concentric'
-  no-important:
-    - 0
-  no-vendor-prefixes:
-    - 0 # this will be fixed with v2: see https://github.com/sasstools/sass-lint/pull/1137
-  nesting-depth:
-    - 1
-    -
-      max-depth: 4
diff --git a/.dev/.stylelintrc.js b/.dev/.stylelintrc.js
new file mode 100644
index 00000000..a754e33b
--- /dev/null
+++ b/.dev/.stylelintrc.js
@@ -0,0 +1,15 @@
+module.exports = {
+  extends: 'stylelint-config-standard',
+  plugins: [
+    "stylelint-scss"
+  ],
+  rules: {
+    "indentation": [2],
+    "number-leading-zero": null,
+    // Replace CSS @ with SASS ones
+    "at-rule-no-unknown": null,
+    "scss/at-rule-no-unknown": true,
+    // not compatible with SASS apparently
+    "no-descending-specificity": null
+  },
+}