Add transformer based on PyTorch TransformerEncoder

Pull Request Title

Description

Wants to merge: vladb/pytorch_transf into main

Type of change

• Bug fix
• New feature
• Enhancement
• Documentation update
• Other (specify right below)

Merge request commits

• Add transformer based on PyTorch TransformerEncoder

Related Issues

Screenshots or GIFs

Checklist

• I have tested the code with the changes manually.
• My code follows the project's style guidelines.
• I have documented my code for others to understand.
• I have updated documentation as needed (including README.md, code comments and doc strings).

Reviewer Guidelines

Additional Notes

Fixes #14 (closed)

@mentions

optimus/models/__init__.py

 from .optimus import OptimusTransformer
+from .pytorch_transformer import PyTorchTransformer