Include license file in the generated wheel package

Created originally on Bitbucket by jdufresne (Jon Dufresne)

Was already merged in Bitbucket before import, marked as merged by the import user

The wheel package format supports including the license file. This is done using the [metadata] section in the setup.cfg file. For additional information on this feature, see:

https://wheel.readthedocs.io/en/stable/index.html#including-the-license-in-the-generated-wheel-file

Helps project comply with its own license:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.