Adding application logs location in the README (#95)

Co-authored-by: ALLARD Antoine <[email protected]>

README.md

@@ -150,6 +150,9 @@ Relatively manual process for now:
   environment.systemPackages = [ globalprotect-openconnect ];
   ```
 
+## Troubleshooting
+
+The application logs can be found at: `~/.cache/GlobalProtect-openconnect/gpclient.log`
 
 ## [License](./LICENSE)
 GPLv3