Duck db demo application

I've had great success using duckdb to speed up R shiny applications, and it would be great to have an example which showed off that integration on the Python side. Some ideas might be:

• An ETL job which sends data to an on-disk duckdb instance which is colocated with the Shiny app
• A Shiny app which uses duckdb to explore a large set of parquet files hosted on S3
• An app which makes blends SQLite and duckdb to make use of multiple writes and columnar reads