This fixes two small code issues that I came across was I was following the tutorial:

First, a syntax error in `todoActions$`.

Secondly, a TypeScript warning in the definition of `useTodos`:
```
Type 'IterableIterator<Todo>' can only be iterated through when using the '--downlevelIteration' flag or with a '--target' of 'es2015' or higher.
```

Replacing `[...todosMap.values()]` with `Array.from(todosMap.values())` makes that warning go away without customising TypeScript from its default value.