DeepChem Updates of October,2023 (Week 2)

Here is a quick summary of DeepChem updates for the 2nd week of October, including the following merged pull requests:
1. Deep dft periodic table Utils: This PR introduces new features and documentation modifications for Deep DFT’s periodic table utilities, addressing an issue.
2.Gan: This PR involves porting of GAN class, adding a new feature to the project.
3. Seq to seq model: This PR addresses several tasks, including modifying the Combine Mean Std. class and tests, restricting the code to function only with tensors (instead of numpy arrays), updating EncoderRNN and DecoderRNN for multilayer support, and adding a SeqToSeq Torch model and tests to improve functionality.