Make device panel scrollable

Previous panel caused main window to resize when device panel was enabled so if the vertical resolution wasn't big enough you'd lose visibility of the toolbar and the text would be noticeably distorted.

frontend/a2fyne/panelDevices.go

@@ -14,17 +14,20 @@ type panelDevices struct {
 func newPanelDevices(s *state) *panelDevices {
 	var pd panelDevices
 	pd.s = s
-	pd.w = container.NewVBox()
+	pd.w = container.NewMax()
+	c := container.NewVBox()
 
 	pd.joystick = newPanelJoystick()
-	pd.w.Add(pd.joystick.w)
+	c.Add(pd.joystick.w)
 
 	var cards = s.a.GetCards()
 	for i, card := range cards {
 		if card != nil && card.GetName() != "" {
-			pd.w.Add(newPanelCard(i, card).w)
+			c.Add(newPanelCard(i, card).w)
 		}
 	}
 
+	pd.w.Add(container.NewVScroll(c))
+
 	return &pd
 }