refs https://github.com/TryGhost/Ghost/issues/14101
- `{{action}}` is deprecated and should be replaced with `{{on}}` and `{{fn}}` with direct use of methods
- switched to calling `ui.setMainClass` action directly
no issue
- initial set up ready for testing use of react components (specifically an editor component for this experiment) inside of Admin
- added `react-editor` route
- duplicated all editor screen files and updated route references where necessary