Add License to PyPI classifiers

[WilliamRoyNelson]

Adds license to PyPI project classifiers

The reason that it is very important for this information to be present is that in an enterprise environment, security tools like Sonatype Nexus IQ are used to manage open source software risk. Nexus IQ specifically can be configured to classify packages according to their license. This prevents developers from inadvertently using licenses like GNU General Public License v2.0 without realizing that they may be legally obligated to make their entire project open source.

My understanding is that Nexus IQ uses the classifiers panel to determine a project's license.
Because Formulaic does not currently include the license in the classifiers panel, Nexus cannot determine the license and treats Formulaic as a high-risk package.

Adding this license information will increase the availability of Formulaic within enterprise environments.

I have made similar PR's for Gradio with excellent results.

[WilliamRoyNelson]

Also, if/when you merge this, can you please also push to PyPI so that the updated information is applied? Thanks!

[matthewwardrop]

Thanks for taking the time to correct this!