fix: add root redirect to /en/ so docs.sharpapi.io resolves

The Nextra locale proxy middleware doesn't run on static exports
with framework: null. Add an explicit Vercel redirect for / → /en.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Mlaz-code

vercel.json

@@ -5,6 +5,7 @@
   "cleanUrls": true,
   "ignoreCommand": "git diff --quiet HEAD^ HEAD -- app/ components/ content/ pages/ public/ styles/ theme.config.tsx next.config.mjs proxy.ts package.json vercel.json",
   "redirects": [
+    { "source": "/", "destination": "/en", "permanent": false },
     { "source": "/streaming", "destination": "/en/streaming/overview", "permanent": true },
     { "source": "/streaming/overview", "destination": "/en/streaming/overview", "permanent": true },
     { "source": "/streaming/:path*", "destination": "/en/streaming/:path*", "permanent": true },