message: update ref guide to include example for arrays
  reference-other-classes(gh-page): add example for ref-arrays
diff: @@ -15,8 +15,11 @@ class Nested {
  }
  class Main {
  - @prop({ ref: Nested })
  + @prop({ ref: Nested }) // for one
  public nested: Ref<Nested>;
  +
  + @arrayProp({ ref: Nested }) // for an array of references
  + public nestedArray: Ref<Nested>[];
  }
  ```
  