Update mime requirement from ^1.6.0 to ^2.3.1

Updates the requirements on [mime](https://github.com/broofa/node-mime) to permit the latest version.
- [Release notes](https://github.com/broofa/node-mime/releases)
- [Changelog](https://github.com/broofa/node-mime/blob/master/CHANGELOG.md)
- [Commits](https://github.com/broofa/node-mime/commits/v2.3.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -28,7 +28,7 @@
     "chalk": "^2.4.1",
     "compression": "^1.7.3",
     "connect": "^3.6.6",
-    "mime": "^1.6.0",
+    "mime": "^2.3.1",
     "morgan": "^1.9.0",
     "opn": "^5.3.0",
     "serve-static": "^1.13.2"