fix: update dependency requirements

[dandhlee]

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Unless the issue you're trying to solve is unique to this specific repository,
please file an issue and/or send changes upstream to the original as well.

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Missed adding sphinxcontrib.napoleon import in setup.py instead of adding it in requirements.txt. Will need to release 0.3.1 to allow docs builds to work across Client Libraries.

Fixes #47

It's a good idea to open an issue first for discussion.

• Tests pass
• Appropriate changes to README are included in PR

[dandhlee]

Adding a test to build without requirements.txt, making sure that the library can build successfully outside of this repo, as if users would have installed through pip.

Testing to make sure that the test works (cached settings seem to flow over, testing to see if that would affect the tests)

[dandhlee]

Tests failed as expected, reverted to original setup as intended. All is good!