feat: handle better not usable items

Fixes #69

sonic-radiance.love/scenes/overworld/screens/mainmenu/items.lua

@@ -174,10 +174,15 @@ function UseWidget:new(scene, pocket, item, widgetId)
   self.pocket = pocket
   self.widgetId = widgetId
   UseWidget.super.new(self, scene, "useMenu", "Use", "")
+  if (not self.itemData.usableOnMap) then
+    self.color = {0.6, 0.6, 0.6}
+  end
 end
 
 function UseWidget:action()
+  if (self.itemData.usableOnMap) then
     self.scene.screens.mainmenu["useItems"](self.scene, self.pocket, self.item, self.widgetId)
+  end
 end
 
 function DropWidget:new(scene, pocket, item, widgetId)