chore(package): update @babel/core to version 7.8.6

Closes #215

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
     "through2": "3.0.1"
   },
   "devDependencies": {
-    "@babel/core": "7.8.4",
+    "@babel/core": "7.8.6",
     "@babel/preset-env": "7.8.4",
     "del": "5.1.0",
     "eslint": "6.8.0",