Len8

Also include the package data in `setup.py`.

The patch includes the `py.typed` file in the package manifest.

Fixes

- [Fix edge-case with docstrings](https://github.com/parafoxia/len8/commit/6d27d6cc4150803492b013881932819f998c832b)

Fixes

* Corrected a typo
* Removed an erroneous error message (21)

Improved output

This release improves len8's output. len8 now groups all problem lines under headers of the file paths.

Toml config support

Additions
- Support for toml config files.
- `__slots__` to `Checker`.
- `Checker.from_config` method.
- `--config` cli flag for passing a custom config file (defaults to `pyproject.toml`)
- `ConfigurationError` for failed configurations.

Changes
- `paths` is no longer a required command line arg, if a config file is used, and `include` is specified.

Valid toml keys:
- include: list of str, the paths to include.
- exclude: list of str, the paths to exclude.
- code-length: int, the maximum code length.
- docs-length: int, the maximum docs length.
- strict: bool, whether or not len8 should raise an error.

**Full Changelog**: https://github.com/parafoxia/len8/compare/v0.5.0...v0.6.0