updated readME to handle secrets for middleware

Author: davidfoo07

README.md

@@ -4,3 +4,8 @@
 ### Note: 
 - You are required to develop individual microservices within separate folders within this repository.
 - The teaching team should be given access to the repositories as we may require viewing the history of the repository in case of any disputes or disagreements. 
+
+
+### for user-service
+- go to firebase project settings > service account > generate new private key
+- rename the downloaded json file into serviceAccountKey.json and paste it the same dir as .env