message: docs(prop): ref: update to include array examples
  fixes typegoose/typegoose#486
diff: @@ -122,19 +122,29 @@ Set which class to use for Reference (this cannot be inferred by the type).
  Example:
  ```ts
  -class Nested {}
  +class Kitten {
  + @prop()
  + public name?: string;
  +}
  -class Parent {
  - @prop({ ref: Nested })
  - public nest: Ref<Nested>;
  +class Cat {
  + // single examples
  + @prop({ ref: () => Kitten })
  + public kitten?: Ref<Kitten>;
  // or
  - @prop({ ref: 'Nested' })
  - public nest: Ref<Nested>;
  + @prop({ ref: 'Kitten' })
  + public kitten?: Ref<Kitten>;
  +
  + // array examples
  + @prop({ ref: () => Kitten })
  + public kittens?: Ref<Kitten>[];
  + // or
  + @prop({ ref: 'Kitten' })
  + public kittens?: Ref<Kitten>[];
  }
  ```
  -The `'Nested'` form is useful to avoid unintuitive errors due to circular dependencies, such as
  -`Error: Options "ref" is set, but is undefined/null!`.
  +The `'Nested'`(as string) form is useful to avoid unintuitive errors due to circular dependencies, such as `Error: Options "ref" is set, but is undefined/null!`.
  ### refPath
  