mobile/UI: open dropdown on any tap for readonly combo box

This seems more intuitive. For editable combo boxes you need to tap on
the indicator, but for non-editable (readonly) ones, you can tap
anywhere and the dropdown is shown.
The code feels a bit clumsy, but seems to work in all cases.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

mobile-widgets/qml/TemplateComboBox.qml

@@ -57,6 +57,15 @@ ComboBox {
 		font: cb.font
 		color: subsurfaceTheme.textColor
 		verticalAlignment: Text.AlignVCenter
+		onPressed: {
+			if (readOnly) {
+				if (cb.popup.opened) {
+					cb.popup.close()
+				} else {
+					cb.popup.open()
+				}
+			}
+		}
 	}
 
 	background: Rectangle {