allow x- properties in schema

demo-api/collections/mycol.yml

@@ -2,19 +2,24 @@ name: mycol
 uploadPath: ../media/mycol
 
 meta:
-  label: { de: mycol, en: mycol }
-  rowIdentTpl: { twig: "{{ title }}" }
-  views:
-    - type: table
-      columns:
-        - title
+    label: { de: mycol, en: mycol }
+    rowIdentTpl: { twig: "{{ title }}" }
+    views:
+        - type: table
+          columns:
+              - title
 
 permissions: !include global/test-permissions.yml
 
+projections:
+    test:
+        select:
+            field1: 1
 
 hooks:
-  get:
-    return:
-      type: javascript
-      file: hooks/mycol/get_return.js
+    get:
+        return:
+            type: javascript
+            file: hooks/mycol/get_return.js
 
+x-additional: test