Add localstorage helper

packages/website/ts/local_storage/state_storage.ts

@@ -0,0 +1,16 @@
+import { localStorage } from 'ts/local_storage/local_storage';
+import { INITIAL_STATE, State } from 'ts/redux/reducer';
+
+const STORAGE_NAME = 'persistedState';
+
+export const stateStorage = {
+    saveState(partialState: Partial<State>): void {
+        localStorage.setObject(STORAGE_NAME, partialState);
+    },
+    getPersistedState(): Partial<State> {
+        return localStorage.getObject(STORAGE_NAME);
+    },
+    getPersistedDefaultState(): State {
+        return { ...INITIAL_STATE, ...stateStorage.getPersistedState() };
+    },
+};