chore(deps): update dependency dotenv to v6

Author: renovate-bot

package-lock.json

@@ -40,7 +40,7 @@
     "@types/node": "8.10.34",
     "@types/source-map-support": "0.4.1",
     "assert-rejects": "0.1.1",
-    "dotenv": "5.0.1",
+    "dotenv": "6.1.0",
     "jscpd": "0.6.24",
     "mocha": "5.2.0",
     "nyc": "11.9.0",