Add `boolean_cast` and `optional_boolean_cast` to the cast submodule and document them
1.3.2
Add tuple_cast to the the cast submodule and document it
1.3.1
As part of a solution for issue 12, add cast submodule with enum_cast helper function
1.3.0
Drop running tests on Python 3.6 since it is end of life.
1.2.1
Enable CI testing on Python 3.10 and 3.11. Use `sys.version_info` to help with imports as mypy plays nicely with this.
1.2.0
Fix `ImportError` for `typing_extensions` on Python <= 3.7, by requiring it as a dependency. This is because `Literal` is used as a type. This did not become part of the built in `typing` module until Python 3.8.