add webview threaded api

pkgs/webview-ui/app/src/index.tsx

@@ -0,0 +1,18 @@
+/* @refresh reload */
+import { render } from "solid-js/web";
+
+import "./index.css";
+import App from "./App";
+
+const root = document.getElementById("app");
+
+// @ts-ignore: add the clan scope to the window object so we can register callbacks for gtk
+window.clan = window.clan || {};
+
+if (import.meta.env.DEV && !(root instanceof HTMLElement)) {
+  throw new Error(
+    "Root element not found. Did you forget to add it to your index.html? Or maybe the id attribute got misspelled?"
+  );
+}
+
+render(() => <App />, root!);