docs: add fumadocs documentation site (#142)

docs/next.config.mjs

@@ -0,0 +1,18 @@
+import { createMDX } from 'fumadocs-mdx/next';
+
+const withMDX = createMDX();
+
+/** @type {import('next').NextConfig} */
+const config = {
+  reactStrictMode: true,
+  async rewrites() {
+    return [
+      {
+        source: '/:path*.mdx',
+        destination: '/llms.mdx/:path*',
+      },
+    ];
+  },
+};
+
+export default withMDX(config);