chore(package): update @types/dotenv to version 6.1.0

Author: greenkeeper[bot]

package.json

@@ -19,7 +19,7 @@
     "@types/body-parser": "^1.16.4",
     "@types/compression": "^0.0.36",
     "@types/cors": "^2.8.3",
-    "@types/dotenv": "^4.0.0",
+    "@types/dotenv": "^6.1.0",
     "@types/graphql": "^0.13.4",
     "@types/helmet": "^0.0.42",
     "@types/jest": "^23.3.9",