ansible_winrm_kerberos_delegation (ansible#22113)

Add a note of how to turn on delegation when using kerberos.

docs/docsite/rst/intro_windows.rst

@@ -253,6 +253,7 @@ Since 2.0, the following custom inventory variables are also supported for addit
 * ``ansible_winrm_realm``: Specify the realm to use for Kerberos authentication.  If the username contains ``@``, Ansible will use the part of the username after ``@`` by default.
 * ``ansible_winrm_transport``: Specify one or more transports as a comma-separated list.  By default, Ansible will use ``kerberos,plaintext`` if the ``kerberos`` module is installed and a realm is defined, otherwise ``plaintext``.
 * ``ansible_winrm_server_cert_validation``: Specify the server certificate validation mode (``ignore`` or ``validate``). Ansible defaults to ``validate`` on Python 2.7.9 and higher, which will result in certificate validation errors against the Windows self-signed certificates. Unless verifiable certificates have been configured on the WinRM listeners, this should be set to ``ignore``
+* ``ansible_winrm_kerberos_delegation``: Set to ``true`` to enable delegation of commands on the remote host when using kerberos.
 * ``ansible_winrm_*``: Any additional keyword arguments supported by ``winrm.Protocol`` may be provided.
 
 .. _windows_system_prep: