Tighten stylelint config. (#27336)

Also improve its formatting.

.stylelintrc

 {
-  "extends": ["stylelint-config-standard", "stylelint-config-recommended-scss"],
+  "extends": [
+    "stylelint-config-standard",
+    "stylelint-config-recommended-scss"
+  ],
   "plugins": [
     "stylelint-order"
   ],
   "rules": {
     "at-rule-empty-line-before": null,
     "at-rule-name-space-after": "always",
+    "at-rule-no-unknown": null,
     "at-rule-no-vendor-prefix": true,
     "at-rule-semicolon-space-before": "never",
     "block-closing-brace-empty-line-before": null,
@@ -19,14 +23,26 @@
     "declaration-no-important": true,
     "font-family-name-quotes": "always-where-recommended",
     "font-weight-notation": [
-      "numeric", {
-        "ignore": ["relative"]
-    }],
+      "numeric",
+      {
+        "ignore": [
+          "relative"
+        ]
+      }
+    ],
     "function-url-no-scheme-relative": true,
     "function-url-quotes": "always",
     "length-zero-no-unit": true,
     "max-empty-lines": 2,
     "max-line-length": null,
+    "media-feature-name-no-unknown": [
+      true,
+      {
+        "ignoreMediaFeatureNames": [
+          "prefers-reduced-motion"
+        ]
+      }
+    ],
     "media-feature-name-no-vendor-prefix": true,
     "media-feature-parentheses-space-inside": "never",
     "media-feature-range-operator-space-after": "always",
@@ -34,9 +50,6 @@
     "no-descending-specificity": null,
     "no-duplicate-selectors": true,
     "number-leading-zero": "never",
-    "media-feature-name-no-unknown": [true, {
-      "ignoreMediaFeatureNames": ["prefers-reduced-motion"]
-    }],
     "order/properties-order": [
       "position",
       "top",
@@ -250,7 +263,35 @@
     ],
     "property-no-vendor-prefix": true,
     "rule-empty-line-before": null,
-    "scss/dollar-variable-default": [true, { "ignore": "local" }],
+    "scss/at-function-named-arguments": "never",
+    "scss/at-function-parentheses-space-before": "never",
+    "scss/at-import-no-partial-leading-underscore": true,
+    "scss/at-mixin-argumentless-call-parentheses": null,
+    "scss/at-mixin-named-arguments": null,
+    "scss/at-mixin-parentheses-space-before": "never",
+    "scss/at-rule-no-unknown": true,
+    "scss/dollar-variable-colon-space-after": "at-least-one-space",
+    "scss/dollar-variable-colon-space-before": "never",
+    "scss/dollar-variable-default": [
+      true,
+      {
+        "ignore": "local"
+      }
+    ],
+    "scss/dollar-variable-no-missing-interpolation": true,
+    "scss/media-feature-value-dollar-variable": null,
+    "scss/no-duplicate-dollar-variables": [
+      null,
+      {
+        "ignoreInsideAtRules": [
+          "if",
+          "mixin"
+        ]
+      }
+    ],
+    "scss/operator-no-newline-after": true,
+    "scss/operator-no-newline-before": true,
+    "scss/operator-no-unspaced": true,
     "selector-attribute-quotes": "always",
     "selector-list-comma-newline-after": "always",
     "selector-list-comma-newline-before": "never-multi-line",
@@ -267,6 +308,7 @@
     "selector-max-universal": 1,
     "selector-no-qualifying-type": true,
     "selector-no-vendor-prefix": true,
+    "shorthand-property-no-redundant-values": true,
     "string-quotes": "double",
     "value-keyword-case": "lower",
     "value-list-comma-newline-after": "never-multi-line",