feat: index gfx according to their tagged action

sonic-radiance.love/scenes/battlesystem/actors/gfx.lua

@@ -11,6 +11,10 @@ function GFX:new(world, x, y, z, spritename, creator, blockProcess, tag)
   self.blockProcess = blockProcess or false
   self.tag = tag or ""
 
+  if (not utils.string.isEmpty(self.tag)) then
+    self:setIndexName(self.tag)
+  end
+
   self.direction = 1
 end