chore(package): update @babel/core to version 7.9.0

Closes #385

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "rollup-plugin"
   ],
   "devDependencies": {
-    "@babel/core": "7.8.7",
+    "@babel/core": "7.9.0",
     "@babel/preset-env": "7.8.7",
     "eslint": "6.8.0",
     "eslint-config-google": "0.14.0",