added step for clearning cache

Author: bhparijat

packages/auth/demo/README.md

@@ -50,6 +50,14 @@ yarn build:deps
 
 This can take some time, and you only need to do it if you've modified the auth package.
 
+You can optionally clear the cache and rebuild using:
+ 
+```bash
+cd auth/demo
+rm -rf node_modules
+yarn build:deps
+```
+
 To run the app locally, simply issue the following command in the `auth/demo` directory:
 
 ```bash