add duckdb connectivity

OpenRefine has connectors for SQLLite, MariaDB, etc., but no connector yet for DuckDB, a highly popular database architecture, especially in the R community.

Proposed solution

Develop new connector logic. Phase one is narrowly scoped to read only operations against a DuckDB database, with no write functionality. A pull request for this is already submitted and will be linked back to this issue.

If phase one is successful, then the contributor would plan to submit a phase two pull request with the supplemental functionality needed to write to DuckDB databases from OpenRefine.

Alternatives considered

There is not yet any OpenRefine connector to DuckDB. Workarounds are possible (e.g., tsv export and import), but add unnecessary extra steps.

Additional context

Already built, tested, and working.