Added settings pullstate and settings store (#223)

* added pullstate

* ran lint and addressed problems

client/src/services/SettingsStore.ts

@@ -0,0 +1,15 @@
+import { Store } from "pullstate";
+
+interface SettingsInterface {
+  isDarkMode: boolean;
+}
+
+export const SettingStore = new Store<SettingsInterface>({
+  isDarkMode: false,
+});
+
+export const toggleTheme = async () => {
+  SettingStore.update((store) => {
+    store.isDarkMode = !store.isDarkMode;
+  });
+};