Mention `favicon.ico` in static file serving docs. (#17540)

docs/basic-features/static-file-serving.md

@@ -16,7 +16,7 @@ function MyImage() {
 export default MyImage
 ```
 
-This folder is also useful for `robots.txt`, Google Site Verification, and any other static files (including `.html`)!
+This folder is also useful for `robots.txt`, `favicon.ico`, Google Site Verification, and any other static files (including `.html`)!
 
 > **Note**: Don't name the `public` directory anything else. The name cannot be changed and is the only directory used to serve static assets.