expose duckdb dialect

[eitsupi]

I noticed that duckdb dialect has been implemented. (Fantastic exclude support!)
However, this is not in the list of dialects available in prql-js and does not seem to be mentioned in the book.

prql/prql-js/src/lib.rs

Lines 110 to 119 in ad543b8

	Dialect::Ansi => D::Ansi,
	Dialect::BigQuery => D::BigQuery,
	Dialect::ClickHouse => D::ClickHouse,
	Dialect::Generic => D::Generic,
	Dialect::Hive => D::Hive,
	Dialect::MsSql => D::MsSql,
	Dialect::MySql => D::MySql,
	Dialect::PostgreSql => D::PostgreSql,
	Dialect::SQLite => D::SQLite,
	Dialect::Snowflake => D::Snowflake,

prql/book/src/queries/header.md

Lines 34 to 43 in ad543b8

	- `sql.ansi`
	- `sql.bigquery`
	- `sql.clickhouse`
	- `sql.generic`
	- `sql.hive`
	- `sql.mssql`
	- `sql.mysql`
	- `sql.postgres`
	- `sql.sqlite`
	- `sql.snowflake`

Originally posted by @eitsupi in #1552