feat(client): add logoff function to terminate connection

src/Client.js

@@ -80,6 +80,10 @@ export class Client extends EventEmitter {
         }
     }
 
+    logoff() {
+        this.#ws.close()
+    }
+
     send(destination, port, data) {
         if(typeof destination === 'bigint') {
             destination = destination.toString(10)