docs: add "Connect to ScyllaDB Cloud Serverless"

[avelanarius]

Add a new documentation page about how to connect to ScyllaDB Cloud Serverless with Python Driver.

[tzach]

@annastuchlik can you please review

[annastuchlik]

@avelanarius There are errors during publication. To address them, you should modify the toctree in the intex.rst file to include the page you added:

.. toctree:: :hidden:

api/index installation getting_started scylla_specific upgrading execution_profiles performance query_paging lwt security user_defined_types object_mapper dates_and_times scylla_cloud scylla_cloud_serverless faq

[annastuchlik]

The content looks good, but the documentation won't publish due to errors. @avelanarius Could you look into it?