Fix testing support in the tutorial

[NicMcPhee]

In S22 they've added an ng test task to the tutorial code (see #6), but it fails because there's no tsconfig.spec.json file. There is a new testing section in the tutorial write-up (not in the tutorial proper, but later in the "Developer Guides" section), and I have no idea if that was there before or not. We should certainly fix things so that ng test runs, and it would be good to incorporate the testing section that into our version of the tutorial as well.