Docs: add quick links
Welcome to GeoPy's documentation!
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+:Documentation: https://geopy.readthedocs.io/
+:Source Code: https://github.com/geopy/geopy
+:Issue Tracker: https://github.com/geopy/geopy/issues
+:Stack Overflow: https://stackoverflow.com/questions/tagged/geopy
+:PyPI: https://pypi.org/project/geopy/
+
.. automodule:: geopy
:members: __doc__
