Update dependency eslint to v6.4.0

Author: renovate-bot

package.json

@@ -77,7 +77,7 @@
     "cross-env": "5.2.0",
     "css-loader": "3.1.0",
     "enzyme": "3.10.0",
-    "eslint": "6.1.0",
+    "eslint": "6.4.0",
     "eslint-config-airbnb-base": "13.2.0",
     "eslint-config-prettier": "6.0.0",
     "eslint-loader": "2.2.1",