gamecore/assets: add activity handling functions

gamecore/modules/assets/init.lua

@@ -276,4 +276,19 @@ function Assets:clearAutotile()
   self.autotile = {}
 end
 
+-- ACTIVITY FUNCTIONS
+-- Handle activity
+
+function Assets:setActivity(activity)
+  self.isActive = activity
+end
+
+function Assets:switchActivity()
+  self.isActive = (self.isActive == false)
+end
+
+function Assets:getActivity()
+  return self.isActive
+end
+
 return Assets