add stylelint for *.overrides amd *.variables and fix indentation

Author: mvorisek

package.json

@@ -26,8 +26,8 @@
   "scripts": {
     "build": "gulp build",
     "changelog": "auto-changelog -p",
-    "lint": "eslint --ext .js . && stylelint \"**/*.{css,less}\"",
-    "lint-fix": "eslint --ext .js . --fix && stylelint \"**/*.{css,less}\" --fix"
+    "lint": "eslint --ext .js . && stylelint \"**/*.{css,less,overrides,variables}\"",
+    "lint-fix": "eslint --ext .js . --fix && stylelint \"**/*.{css,less,overrides,variables}\" --fix"
   },
   "dependencies": {
     "@actions/core": "^1.6.0",