[#451] added websocket connexion (#453)

* [#451] added websocket connexion

* [#451] added tests

* [#451] add missing cleanup for web socket causing memory leaks

src/utils/storage/useSelectedCalendars.ts

@@ -0,0 +1,43 @@
+import { useEffect, useState } from "react";
+
+export function useSelectedCalendars(): string[] {
+  const [calendars, setCalendars] = useState<string[]>(() => {
+    try {
+      return JSON.parse(localStorage.getItem("selectedCalendars") ?? "[]");
+    } catch {
+      return [];
+    }
+  });
+
+  useEffect(() => {
+    const onStorage = (e: StorageEvent) => {
+      if (e.key === "selectedCalendars") {
+        try {
+          setCalendars(JSON.parse(e.newValue ?? "[]"));
+        } catch {
+          setCalendars([]);
+        }
+      }
+    };
+
+    const onLocalChange = (e: CustomEvent<string[]>) => {
+      setCalendars(e.detail);
+    };
+
+    window.addEventListener("storage", onStorage);
+    window.addEventListener(
+      "selectedCalendarsChanged",
+      onLocalChange as EventListener
+    );
+
+    return () => {
+      window.removeEventListener("storage", onStorage);
+      window.removeEventListener(
+        "selectedCalendarsChanged",
+        onLocalChange as EventListener
+      );
+    };
+  }, []);
+
+  return calendars;
+}