Aiosql

The v6.0 release:
- adds support for `pygresql` postgres driver.
- works around `pymysql` and `mysqldb` driver issues.
- adds a few more tests.
- improves the documentation, including badges which look soooo cooool.
- simplifies the development environment, CI configuration.
- updates `myproject.toml`.
- does some cleanup.

- Add Postgres adapter for `pg8000` driver.
- Add `register_adapter`.
- Use more recent CI image.
- Add `flake8` to CI.
- Update documentation.
- Update dependencies.

This release:
- add support for MySQL, on top of Postgres and SQLite
- add support for more drivers : psycopg3, APSW
- refactors the base code significantly to reduce the line count
- CI covers Python 3.7 to 3.10
- add coverage tests to about 100%, including error paths
- updates dependencies and the doc accordingly
- switch to 2-level version numbering

83 94

74 76 78 82