chore(package): update @types/node to version 13.13.4

Closes #92

Author: greenkeeper[bot]

Diff for: package.json

@@ -28,7 +28,7 @@
     "@types/chai": "^4.1.7",
     "@types/express": "^4.17.0",
     "@types/mocha": "5.2.7",
-    "@types/node": "^12.6.8",
+    "@types/node": "^13.13.4",
     "@types/supertest": "2.0.8",
     "chai": "4.2.0",
     "del": "5.0.0",