Add workflow to release CTGAN on PyPI

[gsheni]

Description

As a developer of CTGAN, I want an automated process for releasing CTGAN on PyPI.

Currently, the release process for CTGAN requires a developer to follow the steps in RELEASE.md and upload the distribution package from their local machine. However, this can be automated so that the release process occurs from GitHub Actions. This will result in a more consistent release process (same machine will be used). In addition, others at DataCebo can do the release for CTGAN.

Deliverables

• Add a GitHub workflow that publishes CTGAN source and built distribution to PyPI
• Update RELEASE.md with new instructions

Additional Context

• This GitHub Action can be used: https://github.com/marketplace/actions/pypi-publish