add warning for very large tileset images

lib/Properties.hs

@@ -76,9 +76,10 @@ checkTileset tileset = do
 
   -- reject tilesets unsuitable for workadventure
   unless (tilesetTilewidth tileset == 32 && tilesetTileheight tileset == 32)
-    $ complain $ "Tileset " <> tilesetName tileset <> " must have tile size 32 by 32"
-
+    $ complain $ "Tileset " <> tilesetName tileset <> " must have tile size 32×32"
 
+  unless (tilesetImageheight tileset < 4096 && tilesetImagewidth tileset < 4096)
+    $ warn $ "Tileset " <> tilesetName tileset <> " should not be larger than 4096×4096 pixels in total"
 
 
 -- | Checks a single (custom) property of a layer