Use same return type for both StoreCreator signatures in TS typings

[reklawnos]

When performing a refactor, I noticed that removing the preloadedState param from a createStore call resulted in a different type than calling createStore with preloadedState. This is due to the return type of StoreCreator being slightly different for each signature. Specifically, the one without preloadedState does not include a type param for the action type.

This PR adds the action as a type param for the return type of the createStore function without a preloadedState param, as well as a couple of additional tests in tests/typescript/store.ts that make sure the action type param is included in the return type for both signatures.

[timdorr]

Thanks!