Tox-gh-actions

* Breaking change: When a list of environments to run is specified explicitly, tox-gh-actions now respects it and simply run the given environments without enforcing tox-gh-actions' configuration. 37
* Breaking change: Use `GITHUB_ACTIONS` environment variable instead of `GITHUB_ACTION` for enabling tox-gh-actions. 35
* Support GitHub Actions log lines grouping 36
* Add pytest-cov 28
* Improve documentation

- Add tox 3.12.x support 25
- Use actions/setup-pythonv2 for both README and tox-gh-actions 26
- Run tests with various tox versions 27

- Specify factors using environment variables 20

- PyPy support 18
- Add type hints 14
- Refactoring 15 17

- Bumped the major version to v1. We'll use the semantic versioning.
- Minor changes in documentation, logging, configuration.
- No breaking changes since v0.3.0.

- Python 3.8 support 7
- Run tests on GitHub Actions 5