Fix add_rollback command extension

[johanhelsing]

I think I just made a mistake in my comment here: #58 (comment)

We should just do the same as what .insert does.

This makes the following work:

        commands
            .entity(tilemap_entity)
            .insert(
                TilemapBundle {
                    grid_size,
                    map_type,
                    size: tilemap_size,
                    storage: tile_storage,
                    texture: TilemapTexture::Single(sprites.white_pixel.clone()),
                    tile_size,
                    transform: tilemap_transform.with_z(SHIP_BACKGROUND_LAYER_DEPTH),
                    ..default()
                }
            )
            .add_rollback();

[johanhelsing]

@bushrat011899 fyi