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 Cohere does not currently have a classifiers panel, Nexus cannot determine the license and treats it as a high-risk package.

I also slightly modified the project.urls
I don't know why it doesn't currently display on PyPI, possibly the quotation marks, possibly it should be source instead of Repository The Poetry Docs suggest that repository is valid, but I don't see the link on PyPI. Maybe Repository should be lower case: repository

I used NumPy as a model:
https://github.com/numpy/numpy/blob/main/pyproject.toml#L53-L59

[project.urls]
homepage = "https://numpy.org"
documentation = "https://numpy.org/doc/"
source = "https://github.com/numpy/numpy"
download = "https://pypi.org/project/numpy/#files"
tracker = "https://github.com/numpy/numpy/issues"
"release notes" = "https://numpy.org/doc/stable/release"

[billytrend-cohere]

Thanks for providing this diff @WilliamRoyNelson and the detailed explanation: it sounds fairly critical. We can't directly merge this but @dsinghvi will track this so it can be added to the fern generators that we use!! Will defer to him for prioritisation