Add content on how to call the Python client from a synchronous function

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• I am a Temporal employee

Content Suggestion

The Python Temporal Client methods are all implemented as async.

There are many Temporal users that have existing Python code bases that are only sync, and for these users learning how to invoke the Temporal Client is toil, as they may not be fully versed in asyncio and the event loop. Having documentation that provides a snippet on how to use the Temporal Client from an existing sync method would be very helpful for these folks as part of the getting started experience.