Last minute update of callback URL

app/components/auth/rocketchat/README.md

@@ -1,7 +1,12 @@
 ### Set up
+
 We have used `next-auth` npm package to configure rocketchat authentication. Read more about it [here](https://next-auth.js.org/)
 
-1. set up environment variables for firebase config in `.env.local`
+Before setting up rocket.chat oauth, an oauth app must be created in rocket.chat server. Then, add the callback url in the `redirect uri` list of that app. 
+The callback url is `base-rc4community-url/api/auth/callback/rocket.chat`. For example, if rc4community is running on `http://localhost:3000`, then the callback url should be `http://localhost:3000/api/auth/callback/rocket.chat`.
+
+
+1. set up environment variables for rocketchat legacy oauth config in `.env.local`
 
 ```
 ### BEGIN: Environment variables for RocketChat OAuth legacy