fix(web): add _routes.json to serve /docs as static files on Cloudflare Pages

Author: soranjiro

apps/web/static/_routes.json

@@ -0,0 +1,5 @@
+{
+  "version": 1,
+  "include": ["/*"],
+  "exclude": ["/docs/*", "/docs/**/*", "/icons/*", "/favicon.ico", "/manifest.webmanifest", "/robots.txt"]
+}