chore: fix warning

Author: userquin

README.md

@@ -42,7 +42,7 @@ The module includes support for the following HTTP Client hints:
   - [Sec-CH-Prefers-Reduced-Motion](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Reduced-Motion)
   - [Sec-CH-Prefers-Reduced-Transparency](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-CH-Prefers-Reduced-Transparency)
 
-[![WARNING]]
+[!WARNING]
 > The [HTTP Client hints headers](https://developer.mozilla.org/en-US/docs/Web/HTTP/Client_hints) listed above are still in draft, and only Chromium based browsers support them: Chrome, Edge, Chromium and Opera.
 
 ## Quick Setup