fix(types): getState is not bound to MiddlewareAPI (#4737)

Co-authored-by: Ben Durrant <ben.j.durrant@gmail.com>
Co-authored-by: Tim Dorr <timdorr@users.noreply.github.com>

src/types/middleware.ts

@@ -2,7 +2,7 @@ import type { Dispatch } from './store'
 
 export interface MiddlewareAPI<D extends Dispatch = Dispatch, S = any> {
   dispatch: D
-  getState(): S
+  getState: () => S
 }
 
 /**