Update README.md

Author: rowan-m

README.md

@@ -12,7 +12,7 @@ and v3.
 
 - reCAPTCHA: https://www.google.com/recaptcha
 - This repo: https://github.com/google/recaptcha
-- Hosted demo: https://recaptcha-demo.appspot.com/
+- Hosted demo: https://recaptcha-demo.appspot.com/ ⚠️ **Demo is down! Working on getting it back up asap.**
 - Version: 1.2.4
 - License: BSD, see [LICENSE](LICENSE)