The use of `bevy_ecs_tiled` has resulted in significant performance issues due to the presence of a large number of small collision boxes.

Hello! First of all, thank you for creating this library - it's a very cool project! I'm trying to create a rts game using bevy.When I using `bevy_ecs_tiled` to load a map and build the navmesh, the small box colliders are too many.So it has resulted in significant performance.How can I merge the adjacent collision boxes. English is not my native language.If there are any issues, it is entirely my fault.