Webview: improve linting & typechecks

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

@@ -0,0 +1,9 @@
+import { Component, JSXElement } from "solid-js";
+
+interface LayoutProps {
+  children: JSXElement;
+}
+
+export const Layout: Component<LayoutProps> = (props) => {
+  return <div class="grid grid-cols-8">{props.children}</div>;
+};