chore(package): update cross-env to version 7.0.0

Closes #146

Author: greenkeeper[bot]

package.json

@@ -77,7 +77,7 @@
     "bundlesize": "^0.17.0",
     "concurrently": "^4.0.0",
     "copy-webpack-plugin": "^4.0.1",
-    "cross-env": "^5.1.4",
+    "cross-env": "^7.0.0",
     "cross-spawn": "^6.0.5",
     "css-loader": "^1.0.0",
     "devtron": "^1.4.0",