docs: add known issue

docs/changelog.rst

@@ -196,6 +196,12 @@ Mitogen for Ansible
   for Message(..., 102, ...), my ID is ...* may be visible. These are due to a
   minor race while initializing logging and can be ignored.
 
+* When running with ``-vvv``, log messages will be printed to the console
+  *after* the Ansible run completes, as connection multiplexer shutdown only
+  begins after Ansible exits. This is due to a lack of suitable shutdown hook
+  in Ansible, and is fairly harmless, albeit cosmetically annoying. A future
+  release may include a solution.
+
 * Performance does not scale linearly with target count. This requires
   significant additional work, as major bottlenecks exist in the surrounding
   Ansible code. Performance-related bug reports for any scenario remain