Add example: Streaming results to a database

[Maciej818]

Add example or tutorial to the documentation on streaming results to a database with a custom data sink.
Please note: https://duckdb.org/2023/03/03/json.html for getting started with DuckDB.

• Prepare BQ example
• Check/verify SQL model
• Decide on what API we go forward with

[nicholasjng]

DuckDB is done, BQ is next:

• Schema: https://cloud.google.com/bigquery/docs/reference/standard-sql/data-types
• Table creation: https://cloud.google.com/bigquery/docs/tables#python

[Maciej818]

@nicholasjng I assume that the PR #85 addresses the first task in this ticket ("Prepare BQ example") and the two following are still to be done (" Check/verify SQL model" and "Decide on what API we go forward with") - I created a separate ticket for them #86.
Please shout if my assumption is wrong.