docs: document why we are using the union approach

packages/slonik-dataloaders/src/utilities/batchQueries.ts

@@ -5,7 +5,9 @@ import { type z, type ZodTypeAny } from 'zod';
  * Uses UNION to batch multiple queries that have the same shape.
  * In contrast to using the `json_agg(row_to_json(t))` approach,
  * this has the benefit of using native type parsing and
- * avoid the overhead of serializing and deserializing JSON.
+ * avoids the overhead of serializing and deserializing JSON.
+ * This approach also has the benefit that it is compatible with
+ * Slonik interceptors that validate the shape of the result set.
  */
 export const batchQueries = async <T extends ZodTypeAny>(
   pool: CommonQueryMethods,