Create demo of Text Extensions for Pandas + PySpark

[frreiss]

Create a demonstration of using Text Extensions for Pandas and PySpark together to cover an NLP-related use case.

Some ideas for possible use cases:

• Compute precision and recall for NLP model outputs over a large corpus
• Generate BERT embeddings for an entire corpus in parallel and save the embeddings into a Spark DataFrame
• Load BERT embeddings into a Spark DataFrame, then use Spark to train train multiple classification models in parallel over the embeddings
• Demonstrate serialization of Pandas extension types between Parquet files, Spark DataFrames, and Pandas DataFrames