Add patchState method to the ComponentStore

[markostanimirovic]

Add patchState method to get rid of unnecessary state spreading and replace:

// case 1
this.moviesStore.setState(state => ({
  ...state,
  movies,
}));

// case 2
this.moviesStore.setState(state => ({
  ...state,
  movies: [...state.movies, movie],
}));

with:

// case 1
this.moviesStore.patchState({ movies });

// case 2
this.moviesStore.patchState(state => ({
  movies: [...state.movies, movie],
}));

If accepted, I would be willing to submit a PR for this feature

[x] Yes (Assistance is provided if you need help submitting a pull request)
[ ] No

[alex-okrushko]

@markostanimirovic
Ok, let's look into it. 🙂