message: docs(forms): add FormRecord class to API summary
  Add the missing FormRecord class to the
  Reactive forms API summary which is located under Developer Guides ->
  Forms -> Reactive Forms.
  Fixes
  PR Close
diff: @@ -277,6 +277,7 @@ For complete syntax details, see the API reference documentation for the [Forms
  | `FormGroup` | Manages the value and validity state of a group of `AbstractControl` instances. The group's properties include its child controls. The top-level form in your component is `FormGroup`. |
  | `FormArray` | Manages the value and validity state of a numerically indexed array of `AbstractControl` instances. |
  | `FormBuilder` | An injectable service that provides factory methods for creating control instances. |
  +| `FormRecord` | Tracks the value and validity state of a collection of `FormControl` instances, each of which has the same value type. |
  </table>
  