Sprite packing policy interface. Provide a custom implementation to control which Sprites go into which atlases.
| AllowSequentialPacking | Specifies whether sequential processing of atlas tags is enabled. If enabled, sprite packing tags are processed one by one to reduce memory usage. |
| GetVersion | Return the version of your policy. Sprite Packer needs to know if atlas grouping logic changed. |
| OnGroupAtlases | Implement custom atlas grouping here. |