Class AsyncDismissButton

src/AsyncDialog.cpp:50–55

		setup(message);

		struct AsyncDismissButton : Button {
			AsyncDialog* dialog;
			void onAction(const ActionEvent& e) override {
				dialog->getParent()->requestDelete();
			}
		};
		AsyncDismissButton* const dismissButton = new AsyncDismissButton;
		dismissButton->box.size.x = buttonWidth;
		dismissButton->text = "Dismiss";