chore(package): update cross-env to version 6.0.3

Closes #32

Author: greenkeeper[bot]

package.json

@@ -51,7 +51,7 @@
     "babel-loader": "^7.1.5",
     "babel-preset-react-app": "^3.1.2",
     "babel-runtime": "^6.26.0",
-    "cross-env": "^5.2.0",
+    "cross-env": "^6.0.3",
     "css-loader": "^1.0.0",
     "eslint": "^5.2.0",
     "eslint-config-airbnb": "^17.0.0",