add live game UI with board rendering, timers, and SAN move list

app/static/js/play.js

@@ -0,0 +1,9 @@
+import { PlayApp } from "./play/app.js";
+
+function main() {
+  const app = new PlayApp();
+  window.playApp = app;
+  app.installSocket();
+}
+
+main();