FIX: Add missing transformers documentation

src/caoscrawler/cfood-schema.yml

@@ -17,6 +17,19 @@ cfood:
     macros:
       description: Macro definitions
       type: array
+    Transformers:
+      description: Variable transformer definition
+      type: object
+      additionalProperties:
+        type: object
+        properties:
+          function:
+            type: string
+          package:
+            type: string
+        required:
+          - package
+          - function
   additionalProperties:
     $ref:
       "#/$defs/converter"