Add DuckDB example for R2 Data Catalog (#22694)

Author: jonesphillip

src/content/docs/r2/data-catalog/config-examples/duckdb.mdx

@@ -0,0 +1,42 @@
+---
+title: DuckDB
+pcx_content_type: example
+---
+
+Below is an example of using [DuckDB](https://duckdb.org/) to connect to R2 Data Catalog (read-only). For more information on connecting to R2 Data Catalog with DuckDB, refer to [DuckDB documentation](https://duckdb.org/docs/stable/core_extensions/iceberg/iceberg_rest_catalogs#r2-catalog).
+
+## Prerequisites
+
+- Sign up for a [Cloudflare account](https://dash.cloudflare.com/sign-up/workers-and-pages).
+- [Create an R2 bucket](/r2/buckets/create-buckets/) and [enable the data catalog](/r2/data-catalog/manage-catalogs/#enable-r2-data-catalog-on-a-bucket).
+- [Create an R2 API token](/r2/api/tokens/) with both [R2 and data catalog permissions](/r2/api/tokens/#permissions).
+- Install [DuckDB](https://duckdb.org/docs/installation/).
+  - Note: [DuckDB 1.3.0](https://github.com/duckdb/duckdb/releases/tag/v1.3.0) or greater is required to attach [Iceberg REST Catalogs](https://duckdb.org/docs/stable/core_extensions/iceberg/iceberg_rest_catalogs).
+
+## Example usage
+
+In the [DuckDB CLI](https://duckdb.org/docs/stable/clients/cli/overview.html) (Command Line Interface), run the following commands:
+
+```sql
+-- Install the iceberg DuckDB extension (if you haven't already) and load the extension.
+INSTALL iceberg;
+LOAD iceberg;
+
+-- Create a DuckDB secret to store R2 Data Catalog credentials.
+CREATE SECRET r2_secret (
+    TYPE ICEBERG,
+    TOKEN '<token>'
+);
+
+-- Attach R2 Data Catalog with the following ATTACH statement (read-only).
+ATTACH '<warehouse_name>' AS my_r2_catalog (
+    TYPE ICEBERG,
+    ENDPOINT '<catalog_uri>'
+);
+
+-- Show all available tables.
+SHOW ALL TABLES;
+
+-- Query your Iceberg table.
+SELECT * FROM my_r2_catalog.default.my_iceberg_table;
+```