Implement release workflow in GitHub actions (#734)

- heavily based on @webknjaz's work on https://github.com/cherrypy/cheroot/blob/b2c619f3e60682b9405a87cea48e8d30801b6048/.github/workflows/ci-cd.yml
- create package before running tests, run tests against same package that will be published
- run nightly tests
- publish package to test pypi for commits to master
- publish package to pypi using workflow_dispatch
- create git tag and github release after successful tests on workflow_dispatch
- add twine as explicit dev requirement

Co-authored-by: Sviatoslav Sydorenko <wk@sydorenko.org.ua>

Author: Nothing4You