docs: add missing meta property of cube (#7740) (#7748) Thanks @hannosgit !

Author: hannosgit

docs/pages/reference/rest-api.mdx

@@ -152,6 +152,7 @@ Response
 - `cubes` - Array of cubes
   - `name` - Codename of the cube
   - `title` - Human-readable cube name
+  - `meta` - Custom metadata
   - `measures` - Array of measures defined within this cube
   - `dimensions` - Array of dimensions defined within this cube
   - `segments` - Array of segments defined within this cube
@@ -175,6 +176,12 @@ Example response:
     {
       "name": "Users",
       "title": "Users",
+      "meta": {
+          "someKey": "someValue",
+          "nested": {
+            "someKey": "someValue"
+          }
+      },
       "connectedComponent": 1,
       "measures": [
         {