Update dependency core-js to v2.6.2 (#306)

Author: renovate[bot]

package-lock.json

@@ -40,7 +40,7 @@
     "babel-eslint": "10.0.1",
     "babel-loader": "8.0.5",
     "clean-webpack-plugin": "1.0.0",
-    "core-js": "2.6.1",
+    "core-js": "2.6.2",
     "cross-env": "5.2.0",
     "css-loader": "2.1.0",
     "eslint": "5.12.0",