message: docs/deprecations: add note about working around AppTheme type
diff: @@ -54,3 +54,10 @@ const darkTheme = {
  ),
  };
  ```
  +
  +Note that the existing `AppTheme` type still requires the `theme` property to be
  +set since it's the type that's consumed in the `AppThemeApi`, and it would be a
  +breaking change to make `theme` optional. This means that if you currently
  +construct the themes that you pass on to `createApp` using `AppTheme` as an
  +intermediate type, you will need to work around this in some way, for example by
  +passing the themes to `createApp` more directly.
  