frontend: add svelte frontend

frontend/src/routes/sverdle/how-to-play/+page.ts

@@ -0,0 +1,9 @@
+import { dev } from '$app/environment';
+
+// we don't need any JS on this page, though we'll load
+// it in dev so that we get hot module replacement
+export const csr = dev;
+
+// since there's no dynamic data here, we can prerender
+// it so that it gets served as a static asset in production
+export const prerender = true;