added return AppStateType to useAppState web implementation

src/hooks/useAppState/index.ts

@@ -1,4 +1,8 @@
-export default function useAppState() {
+import type AppStateType from './types';
+
+function useAppState(): AppStateType {
     // Since there's no AppState in web, we'll always return isForeground as true
     return {isForeground: true, isInactive: false, isBackground: false};
 }
+
+export default useAppState;