Enable Prettier formatting of .css files

Author: robertknight

package.json

@@ -64,8 +64,8 @@
     "build-pattern-lib": "yarn gulp bundle-css && yarn rollup -c rollup.config.js",
     "typecheck": "tsc --build src/tsconfig.json",
     "lint": "eslint --cache .",
-    "checkformatting": "prettier --cache --check '**/*.{js,scss,ts,tsx,md}'",
-    "format": "prettier --cache --list-different --write '**/*.{js,scss,ts,tsx,md}'",
+    "checkformatting": "prettier --cache --check '**/*.{css,js,scss,ts,tsx,md}'",
+    "format": "prettier --cache --list-different --write '**/*.{css,js,scss,ts,tsx,md}'",
     "test": "gulp test",
     "push": "yarn build && yalc push"
   },