Merge pull request #26 from miyabayt/renovate/helmet-6.x

Update dependency helmet to v6

Author: miyabayt

package-lock.json

@@ -20,7 +20,7 @@
     "express-mysql-session": "2.1.8",
     "express-session": "1.17.3",
     "express-validator": "6.14.2",
-    "helmet": "3.23.3",
+    "helmet": "6.0.0",
     "html5shiv": "3.7.3",
     "http-errors": "1.8.1",
     "lodash": "4.17.21",