Add documentation about dbt-duckdb adapter

[TylerHillery]

Description & motivation

Related to issue #1489

Prerelease docs

Is this change related to an unreleased version of dbt?

• No: please ensure the base branch is current

Checklist

If you added new pages (delete if not applicable):

• The page has been added to website/sidebars.js
• The new page has a unique filename

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[dataders]

@TylerHillery very much appreciate your contribution here -- especially the written explanation of what connection configurations exist.

My first thought was to ask you to make a duckdb-config.md page, but looking at duckdb's CREATE TABLE docs, it doesn't seem there are no special configuration considerations for tables and view materializations.

Here's my underinformed brain thumb of things that might require docs:

• database-wide configuration options e.g. threads? might that correspond to the number of threads that dbt might want to use?
• VIRTUAL and STORED columns (though IIUC, STORED isn't possible yet?
• the "dbtonic" way of "importing" from file formats like parquet. is it via dbt-external-tables? Or is best practice that a dbt user should make the models at the top of the tag use the FROM filename.parquet instead of the {{ source(filename) }} convention?
  cc: @jwills aka the Willy Wonka of Data

[TylerHillery]

@dataders I appreciate the feedback. I will do some more research on these topics to see what I can do for a duckdb-config.md file.

[dataders]

@dataders I appreciate the feedback. I will do some more research on these topics to see what I can do for a duckdb-config.md file.

sweet! in the meantime I'll merge this PR, and you can open another when you're ready to add more config info. Generally, my stoke level is high for both duck db and dbt-duckdbt so I'm happy to support where able.