Add SPTSv2
### Model description

SPTSv2 is the latest SOTA text spotting model from Bytedance. Given that we already support DETR, should be a breeze to support this model as well.

SPTSv2 is an improvement over the first version: https://github.com/shannanyinxiang/SPTS.

### Open source status

- [X] The model implementation is available
- [X] The model weights are available

### Provide useful links for the implementation

https://github.com/bytedance/SPTSv2
Hi @NielsRogge can I please contribute this model? 