Update dependency eslint to v5.6.0

Author: renovate-bot

package.json

@@ -16,7 +16,7 @@
     "probot": "7.0.1"
   },
   "devDependencies": {
-    "eslint": "5.3.0",
+    "eslint": "5.6.0",
     "eslint-plugin-prettier": "2.6.2",
     "jest": "23.5.0",
     "localtunnel": "1.9.0",