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

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

docs/configuring-playbook-bridge-heisenbridge.md

@@ -77,3 +77,7 @@ Help is available for all commands with the `-h` switch.
 You can also learn the basics by watching [this demonstration video](https://www.youtube.com/watch?v=nQk1Bp4tk4I).
 
 If you encounter issues or feel lost you can join the project room at [#heisenbridge:vi.fi](https://matrix.to/#/#heisenbridge:vi.fi) for help.
+
+## 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-heisenbridge`.