Adds an action object to the action group and sets up the accelerator.
If accelerator is null, attempts to use the accelerator associated with the stock_id of the action.
Accel paths are set to <Actions>/group-name/action-name.
the action to add
the accelerator for the action, in the format understood by gtk.global.acceleratorParse, or "" for no accelerator, or null to use the stock accelerator
Adds an action object to the action group and sets up the accelerator.
If accelerator is null, attempts to use the accelerator associated with the stock_id of the action.
Accel paths are set to <Actions>/group-name/action-name.