fix: Add the missing @types/superagent

Author: leeyeh

package-lock.json

@@ -41,6 +41,7 @@
     "@pollyjs/adapter-node-http": "^2.6.2",
     "@pollyjs/core": "^2.6.2",
     "@pollyjs/persister-fs": "^2.6.2",
+    "@types/superagent": "^4.1.7",
     "babel-core": "^6.4.0",
     "babel-loader": "^7.0.0",
     "babel-plugin-istanbul": "^2.0.0",