feat: sync with web-shim-codegen v3.0.1

## Changes

- Add `Language` functions to `User` model (Resolves #143)
- Add missing types `UserChangeEvent` & new properties (OneSignal/web-shim-codegen@6ae24c1)
- Update function templates to support non-void return types (OneSignal/web-shim-codegen@a3ac32f)

See: https://github.com/OneSignal/web-shim-codegen/releases/tag/3.0.1

Author: OneSignal