fix(package): update @types/dotenv to version 6.1.1

Closes #109

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
     "@types/cookie-parser": "^1.4.1",
     "@types/cors": "^2.8.3",
     "@types/debug": "0.0.30",
-    "@types/dotenv": "^4.0.2",
+    "@types/dotenv": "^6.1.1",
     "@types/express": "^4.11.1",
     "@types/lowdb": "^1.0.0",
     "@types/mime": "^2.0.0",