fix(package): update superagent to version 5.2.1

Closes #31

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "@types/debug": "4.1.4",
     "@types/superagent": "4.1.3",
     "debug": "4.1.1",
-    "superagent": "5.1.0",
+    "superagent": "5.2.1",
     "axios": "0.19.0"
   },
   "devDependencies": {