Update docs/configuring-playbook-conduwuit.md: add the common section "Troubleshooting"

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/configuring-playbook-conduwuit.md

@@ -91,3 +91,7 @@ Then, send its content to the existing admin room:
     sender_localpart: _bot_signalbot
     url: http://matrix-mautrix-signal:29328
     ```
+
+## Troubleshooting
+
+As with all other services, you can find the logs in [systemd-journald](https://www.freedesktop.org/software/systemd/man/systemd-journald.service.html) by logging in to the server with SSH and running `journalctl -fu matrix-conduwuit`.