add baseline fredformer

[superarthurlx]

Paper: Fredformer: Frequency Debiased Transformer for Time Series Forecasting
Link: https://arxiv.org/pdf/2406.09009
Ref Official Code: https://github.com/chenzRG/Fredformer
Venue: KDD 2024
Task: Long-term Time Series Forecasting
                       原文MAE MSE |  复现 MAE MSE

ettm1(96-96): 0.361 0.326 | 0.357 0.325
weather(96-96): 0,207 0.163 | 0.193 0.157
weather(96-192): 0.251 0.211 | 0.239 0.205
复现结果只跑了一次，结果都比原文的结果好一点，应该可信

[zezhishao]

感谢！