Preparing to publish Python wheel, and moving python examples to python-examples/ top-level dir

[arschles]

Preparing the python/pyproject.toml manifest to build and publish wheels to pypi.org, then publishing the first version. Also, moving code from python/examples to a new top-level python-examples/ directory.

[phranzia]

Edit: This example demonstrates how to customize the PubMedQA benchmark. If you do not need custom behavior, you can run PubMedQA as a built-in benchmark.

Delete this: his file demonstrates how to implement a custom Quantiles eval using PubMedQA.

Although PubMedQA is available as a built-in benchmark in the qt CLI, this example is not used by
the built-in implementation.