add indexof

Author: Scott Watkins

package-lock.json

@@ -44,6 +44,7 @@
     "fs-extra": "^8.1.0",
     "html-webpack-plugin": "4.0.0-beta.11",
     "identity-obj-proxy": "3.0.0",
+    "indexof": "0.0.1",
     "jest": "24.9.0",
     "jest-environment-jsdom-fourteen": "1.0.1",
     "jest-resolve": "24.9.0",