Add a config for `resourceAssignmentClick` event to change on dblclick

[chuckn0rris]

Should be possible to configure component and make resourceAssignmentClick to be resourceAssignmentDblClick

Forum post

Lastly, is there any chance a corresponding double click event could be implemented for the resourceAssignmentClick (Gantt.view.GanttBase#event-resourceAssignmentClick) event? This would make accessible design much easier in our implementation of the column.

Thanks, Callum