Bump cross-env from 5.2.1 to 7.0.3

Bumps [cross-env](https://github.com/kentcdodds/cross-env) from 5.2.1 to 7.0.3.
- [Release notes](https://github.com/kentcdodds/cross-env/releases)
- [Changelog](https://github.com/kentcdodds/cross-env/blob/master/CHANGELOG.md)
- [Commits](https://github.com/kentcdodds/cross-env/compare/v5.2.1...v7.0.3)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -25,7 +25,7 @@
     "babel-runtime": "^6.26.0",
     "case-sensitive-paths-webpack-plugin": "^2.1.1",
     "copy-webpack-plugin": "^4.2.0",
-    "cross-env": "^5.1.0",
+    "cross-env": "^7.0.3",
     "css-loader": "^0.28.7",
     "eslint": "^4.9.0",
     "eslint-config-airbnb-base": "^12.1.0",