Add Sites worker entrypoint

build/prepare-sites-build.mjs

@@ -0,0 +1,11 @@
+import { copyFile, mkdir } from 'node:fs/promises';
+import { resolve } from 'node:path';
+
+const root = process.cwd();
+const serverDirectory = resolve(root, 'dist', 'server');
+
+await mkdir(serverDirectory, { recursive: true });
+await copyFile(
+    resolve(root, 'worker', 'index.js'),
+    resolve(serverDirectory, 'index.js'),
+);