Add Dialog and DialogButtonBox

Dialog {
    title: "Standard buttons"
    standardButtons: Dialog.Ok | Dialog.Cancel
    onAccepted: { }
    onRejected: { }
}

Dialog {
    title: "Custom buttons"
    footer: DialogButtonBox {
        Button { text: "Custom 1"; DialogButtonBox.buttonRole: DialogButtonBox.AcceptRole }
        Button { text: "Custom 2"; DialogButtonBox.buttonRole: DialogButtonBox.RejectRole }
    }
    onAccepted: { }
    onRejected: { }
}