test adding extension description

[isaacbrodsky]

For use with https://github.com/duckdb/duckdb/compare/main...isaacbrodsky:duckdb:loaded-extensions-description?expand=1

D select extension_name, description from duckdb_extensions() where extension_name = 'h3';
┌────────────────┬────────────────────────────────────────────────────────────┐
│ extension_name │                        description                         │
│    varchar     │                          varchar                           │
├────────────────┼────────────────────────────────────────────────────────────┤
│ h3             │ Hierarchical hexagonal geospatial indexing system (v4.1.0) │
└────────────────┴────────────────────────────────────────────────────────────┘

[carlopi]

Hi! I had a version of this https://github.com/carlopi/duckdb/pull/67/files, but was not ready to be merged for 1.0.0.

In some version of this will made it in for 1.1.0, feel free to send a PR, we can always iterate on.