doc: Add MIT License to classifiers

To address pyroma warning

> The license 'MIT' specified is not listed in your classifiers.

Signed-off-by: Kevin Locke <[email protected]>

Author: kevinoid

setup.cfg

@@ -28,6 +28,7 @@ project_urls =
 classifiers =
     Development Status :: 3 - Alpha
     Intended Audience :: Developers
+    License :: OSI Approved :: MIT License
     Operating System :: OS Independent
     Programming Language :: Python
     Programming Language :: Python :: 3