"Cannot find module" error when starting an angular demo app

[jnorkus]

To reproduce:

1. Download the repo zip file and extract
2. npm setup
3. npm add
4. npm start
5. apps.demo-angular.android

Result:

ERROR in ../../tools/demo/test-package/index.ts:2:18 - error TS2307: Cannot find module '@nativescript/test-package' or its corresponding type declarations.

2 import {  } from '@nativescript/test-package';