Create SubscribeAPI method to make it easier to update deeply nested state

[hjrdave]

This is just in case you want to have multiple states within one state object for groups.

Possible example:
Store.updateNested(action: string, targetProp: string, dispatchValue: any)

Not sure on name.

[hjrdave]

updateDeep is a possible name for the method

[hjrdave]

make sure you make the state immutable. Do not mutate it.

[hjrdave]

Store.deepUpdate()