Switch build from SQLite to DuckDB for penguins DB

[Pavan0277]

1. Replace sqlite3 CLI with duckdb in common.mk for in-repo query targets.
2. Add create_penguins_duckdb.py to generate DuckDB-format db/penguins.db.
3. command in ./Makefile that generates db/penguins.db

[Pavan0277]

Hi @gvwilson, could you please review this PR when you get a chance and merge it if everything looks good? Thanks!

[gvwilson]

Thanks @Pavan0228 - I'll try it out and leave feedback this week.

[gvwilson]

Hi @Pavan0228 - after looking through this and thinking about how many other things would have to change, I've decided to stick with SQLite for now, and to create another short lesson on DuckDB similar to the one on PostgreSQL. I'll keep this PR open for reference, and may merge it into the branch where I do the DuckDB lesson so that your contribution shows up in the Git history. Thanks again for creating it - I appreciate it a lot.