docs/system/devices/usb: Add CanoKey to USB devices examples

Signed-off-by: Hongren (Zenithal) Zheng <i@zenithal.me>
Message-Id: <YoY6o+QFhzA7VHcZ@Sun>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

docs/system/devices/usb.rst

@@ -199,6 +199,10 @@ option or the ``device_add`` monitor command. Available devices are:
 ``u2f-{emulated,passthru}``
    Universal Second Factor device
 
+``canokey``
+   An Open-source Secure Key implementing FIDO2, OpenPGP, PIV and more.
+   For more information, see :ref:`canokey`.
+
 Physical port addressing
 ^^^^^^^^^^^^^^^^^^^^^^^^