selectManyMenu with showCheckbox="true" is not keyboard friendly

[hungar]

The "Advanced" example in the showcase has checkboxes for the items but there doesn't appear to be any way to select items from the list other than using the mouse. This is not an accessible (ADA Section 508 compliant) user interface. Is there any way to work around this limitation? If not, maybe there is an enhancement request needed to make it compliant.

[Melloware]

Already an open ticket: https://github.com/primefaces/primefaces/issues/1435