Readable and Writable helpers for String, HashMap and HashSet (#4834)

* Add more read/write methods for string signals

* add helpers for HashMap and HashSet as well

* fix typo

* fix conflicting string and str extensions

* fix counters example

examples/01-app-demos/websocket_chat.rs

@@ -46,7 +46,7 @@ fn app() -> Element {
     use_future(move || async move {
         while let Ok(msg) = socket.recv().await {
             match msg {
-                ServerEvent::ReceiveMessage(message) => message_list.write().push(message),
+                ServerEvent::ReceiveMessage(message) => message_list.push(message),
                 ServerEvent::Connected { messages } => message_list.set(messages),
             }
         }