Use relative link for ws on test page

src/main.rs

@@ -55,7 +55,7 @@ fn index() -> Html<&'static str> {
             sendForm.hidden = false;
             msgsArea.hidden = false;
             msgInput.focus();
-            ws = new WebSocket("ws://localhost:2000/api/ws");
+            ws = new WebSocket("ws://" + window.location.host + "/api/ws");
             ws.onmessage = function(event) {
                 msgsArea.value += event.data + "\r\n";
             }