Add TEFN

[WenjieDu]

1. Model description

As an interesting work, TEFN should be included in PyPOTS, and could start from the imputation task. The author @ztxtech would like to make contributions to accomplish this and maintain the model in the future. Thanks to Tianxiang.

@article{zhan2024tefn,
  title={Time Evidence Fusion Network: Multi-source View in Long-Term Time Series Forecasting},
  author={Zhan, Tianxiang and He, Yuanpeng and Li, Zhen and Deng, Yong},
  journal={arXiv preprint arXiv:2405.06419},
  year={2024}
}

2. Check open-source status

• The model implementation is publicly available

3. Provide useful information for the implementation

https://github.com/ztxtech/Time-Evidence-Fusion-Network