MDL-79003 js: Bump stylelint and components

Stylelint 15 deprecates a heap of rules which will be removed in 16.

We can't use 16 because it's ESM and requires a big restructure of our
build process.

We can temporarily silence the deprecations and then when we update our
build tooling we can make use of @stylistic/stylelint-plugin to add the
rules back.

This commit:
- bumps stylelint and related dependencies accordingly
- fixes issues identified with newer sniffs
- temporarily silences deprecation warnings

package.json

@@ -27,7 +27,7 @@
     "grunt-eslint": "24.0.0",
     "grunt-rollup": "^11.9.0",
     "grunt-sass": "3.1.0",
-    "grunt-stylelint": "0.15.0",
+    "grunt-stylelint": "^0.19.0",
     "hugo-bin": "^0.80.2",
     "hugo-lunr-indexer": "^1.1.3",
     "jsdoc": "^4.0.2",
@@ -35,13 +35,13 @@
     "jshint": "^2.13.4",
     "jstoxml": "^3.2.3",
     "npm-run-all": "^4.1.5",
+    "postcss-scss": "^4.0.9",
     "rollup-plugin-terser": "^7.0.2",
     "sass": "^1.58.3",
     "semver": "7.3.5",
     "shifter": "https://github.com/andrewnicols/shifter/archive/v1.2.0_moodle-0.tar.gz",
-    "stylelint": "13.3.3",
-    "stylelint-checkstyle-formatter": "0.1.2",
-    "stylelint-csstree-validator": "1.8.0",
+    "stylelint": "^15.11.0",
+    "stylelint-csstree-validator": "^3.0.0",
     "xpath": "0.0.32"
   },
   "engines": {