Add publish to pypi action

[Erotemic]

Addresses #86

This adds the standard pypi publishing action integrated into github. To make this work the maintainers will need to take the following steps:

1. Ensure there is a PyPI account available to manage the every-eval-ever project.

   • Either an existing maintainer must already own or maintain the project on PyPI, or someone must create the project there on first release.
   • At least one maintainer should have enough PyPI access to configure project settings.

2. Configure a Trusted Publisher for every-eval-ever on PyPI.

   • PyPI project: every-eval-ever
   • GitHub owner: evaleval
   • Repository: every_eval_ever
   • Workflow file: publish.yaml
   • Environment name: pypi

3. Optionally create/configure the pypi GitHub environment if you want environment protection rules. This is recommended, but not strictly required.

Once those steps are complete, creating and pushing a new version tag will both create the GitHub release and publish the package to PyPI.

[Erotemic]

I also added badges to the README, which will look nice once there is a version on pypi. See one of my repos for what these badges look like: https://github.com/Erotemic/xdoctest

[nelaturuharsha]

Pending chat on how to handle trusted publishing will move to merge. Thanks :D