Bump superagent from 3.8.2 to 5.2.1

Bumps [superagent](https://github.com/visionmedia/superagent) from 3.8.2 to 5.2.1.
- [Release notes](https://github.com/visionmedia/superagent/releases)
- [Changelog](https://github.com/visionmedia/superagent/blob/master/HISTORY.md)
- [Commits](https://github.com/visionmedia/superagent/compare/v3.8.2...v5.2.1)

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

package.json

@@ -54,7 +54,7 @@
     "react": "^16.12.0",
     "react-dom": "^16.3.3",
     "shortid": "^2.2.4",
-    "superagent": "^3.8.2",
+    "superagent": "^5.2.1",
     "vitreum": "^4.10.1"
   },
   "devDependencies": {