Add ReduxInitAction interface to type definitions

[merrywhether]

In attempting to model of all of the action types in our TypeScript app, the @@redux/INIT action is the odd one out, as it originates from the redux code itself. It'd be great if that were part of the redux type definitions themselves instead.

[jimbolla]

I believe INIT is considered a private and not intended to be exposed to the outside. There's a work item to make the type random. #1736 (comment)

[mfollett]

@jimbolla If you wanted to do a discriminated union of actions what would you use to model the internal actions, then?

[jimbolla]

I blieve the idea is that a reducer can handle an unknown action.

[mfollett]

But, in TS you'd either need to model that unknown action with a specific shape or have a catchall that has no shape and then you lose your type safety, unless there's something I'm missing. There are gradients, you could end with any or {type: string} which would give you various levels of safety loss, but that doesn't seem great.

[mfollett]

Actually, if the type is going to be random, the best you can go with is just the {type: any} anyway.

[TrySound]

Actions shoudn't be random, but init action is internal one which do not required to be public. Typescript is for static analysis of your code, not libraries code.

[merrywhether]

Cool, sounds like a bail then. Thanks for the pointers.