Add npm script to run prettier on whole repo (#1661)

Author: hsubox76

package.json

@@ -32,7 +32,8 @@
     "test:saucelabs": "karma start config/karma.saucelabs.js --single-run",
     "docgen:js": "node scripts/docgen/generate-docs.js --api js",
     "docgen:node": "node scripts/docgen/generate-docs.js --api node",
-    "docgen": "npm run docgen:js; npm run docgen:node"
+    "docgen": "npm run docgen:js; npm run docgen:node",
+    "prettier": "prettier --config .prettierrc --write '**/*.{ts,js}'"
   },
   "repository": {
     "type": "git",