Document that "borgmatic borg create" bypasses monitoring hooks (#882).

docs/how-to/run-arbitrary-borg-commands.md

@@ -133,6 +133,8 @@ borgmatic's `borg` action is not without limitations:
    borgmatic action. In this case, only the Borg command is run.
  * Unlike normal borgmatic actions that support JSON, the `borg` action will
    not disable certain borgmatic logs to avoid interfering with JSON output.
+ * The `borg` action bypasses most of borgmatic's machinery, so for instance
+   monitoring hooks will not get triggered when running `borgmatic borg create`.
  * <span class="minilink minilink-addedin">Prior to version 1.8.0</span>
    borgmatic implicitly injected the repository/archive arguments on the Borg
    command-line for you (based on your borgmatic configuration or the