Update docs/configuring-playbook-bridge-beeper-linkedin.md: add a note about variable names

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

docs/configuring-playbook-bridge-beeper-linkedin.md

@@ -18,6 +18,8 @@ There are some additional things you may wish to configure about the bridge.
 
 See [this section](configuring-playbook-bridge-mautrix-bridges.md#extending-the-configuration) on the [common guide for configuring mautrix bridges](configuring-playbook-bridge-mautrix-bridges.md) for details about variables that you can customize and the bridge's default configuration, including [bridge permissions](configuring-playbook-bridge-mautrix-bridges.md#configure-bridge-permissions-optional), [encryption support](configuring-playbook-bridge-mautrix-bridges.md#enable-encryption-optional), [relay mode](configuring-playbook-bridge-mautrix-bridges.md#enable-relay-mode-optional), [bot's username](configuring-playbook-bridge-mautrix-bridges.md#setting-the-bot-s-username-optional), etc.
 
+**Note**: when following the guide to configure the bridge, make sure to replace `_mautrix_SERVICENAME_` in the variable names with `_beeper_linkedin_`.
+
 ## Installing
 
 After configuring the playbook, run it with [playbook tags](playbook-tags.md) as below: