message: feat(frontend): readme update
diff: We're working to stabilize the 2.0 API, and until then there will be breaking changes.
  +Note that this package contains two vue apps, the main frontend (located under @/main), and the viewer embed app (@/embed).
  +
  Notes:
  - In **development** mode, the Speckle Server will proxy the frontend from `localhost:3000` to `localhost:8080`. If you don't see anything, ensure you've run `npm run serve` in the frontend package.
  