Document PRQL extension

extensions/prql/description.yml

@@ -5,10 +5,38 @@ extension:
   language: C++
   build: cmake
   license: MIT
-  excluded_platforms: ""
   maintainers:
     - ywelsch
 
 repo:
   github: ywelsch/duckdb-prql
   ref: 60854f0f1c90a3e90786ff353b0ac99629e26300
+
+docs:
+  hello_world: |
+    let invoices = s"select * from 'https://raw.githubusercontent.com/PRQL/prql/0.8.0/prql-compiler/tests/integration/data/chinook/invoices.csv'"
+    let customers = s"select * from 'https://raw.githubusercontent.com/PRQL/prql/0.8.0/prql-compiler/tests/integration/data/chinook/customers.csv'"
+    from invoices
+    filter invoice_date >= @1970-01-16
+    derive {
+      transaction_fees = 0.8,
+      income = total - transaction_fees
+    }
+    filter income > 1
+    group customer_id (
+      aggregate {
+        average total,
+        sum_income = sum income,
+        ct = count total,
+      }
+    )
+    sort {-sum_income}
+    take 10
+    join c=customers (==customer_id)
+    derive name = f"{c.last_name}, {c.first_name}"
+    select {
+      c.customer_id, name, sum_income
+    }
+    derive db_version = s"version()"
+  extended_description: |
+    The PRQL extension adds support for the [Pipelined Relational Query Language](https://prql-lang.org).