Drop unnecessary namespaces

[rjz]

E.g. in src/reducers/Store, the Store namespace can be flattened out:

export type Counter = {
  value: number,
}

export type All = {
  counter: Counter,
  isSaving: boolean,
  isLoading: boolean,
  error: string,
}

...and its effect still captured nicely via import:

import * as store from './src/reducers/store'

const state: store.All = // ...

HT @egmanoj for the suggestion!