Versioned documentation

**Is your feature request related to a problem? Please describe.**
Right now the documentation on https://pydeequ.readthedocs.io/en/latest/ is only available for the latest version of PyDeequ. Due to various constraints we might be using an older version of the package, so I'd like to be able to see the docs for that particular version.

**Describe the solution you'd like**
Enable versioning for readthedocs: https://docs.readthedocs.io/en/stable/versions.html