version 0.8.0

This makes the entire library compatible with PEP-561, so that it can now be used with a static type checker like mypy. The codebase has been reformatted with black and isort, and the tags field of a PlanQuery now takes a list of strings, rather than a single string containing the tags separated by commas and spaces. pdf is now the only return format which returns bytes; native returns a dataclass and all other formats return a UTF-8 string.

The changelog has also been updated to include the changes of version 0.5.0 and earlier. A pre-commit file has been added to ensure all checks will pass before committing.