[ngrx] Redux basics

- recreate the concept
    - state
    - reducer
    - dispatch
    - Store

- middleware

```
Store {
  state

  private reducer(state, action) {
    switch(action) {

        return state.copy();

    }
  }

  dispatch(action) {
     return reducer(state, action)
  }
}

action: {type: string, payload: any}
```