Bump mongoose from 4.13.19 to 5.7.7

Bumps [mongoose](https://github.com/Automattic/mongoose) from 4.13.19 to 5.7.7.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/History.md)
- [Commits](Automattic/mongoose@4.13.19...5.7.7)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package.json

@@ -18,7 +18,7 @@
     "ejs": "^2.5.6",
     "express": "~4.14.1",
     "jade": "~1.11.0",
-    "mongoose": "^4.10.3",
+    "mongoose": "^5.7.7",
     "morgan": "~1.7.0",
     "serve-favicon": "~2.3.2",
     "vue": "^2.2.6",