add cover image

Author: garronej

README.md

@@ -1,5 +1,5 @@
 <p align="center">
-    <img src="https://user-images.githubusercontent.com/6702424/80216211-00ef5280-863e-11ea-81de-59f3a3d4b8e4.png">  
+    <img src="https://github.com/codegouvfr/dsfr-react/releases/download/assets/dsfr-react_repo-card.png">  
 </p>
 <p align="center">
     <i> React implementation of the <a href="https://www.systeme-de-design.gouv.fr/">DSFR</a> </i>
@@ -35,7 +35,7 @@ yarn start_cra  # For testing in in a Create React App setup
 yarn start_next # For testing in a Next.js setup
 ```
 
-> ⚠️: When you want to import assets from the `./dsfr/` directory
+> When you want to import assets from the `./dsfr/` directory
 > you must assume it's located in `./src/dsfr` because it's where
 > it's going to be relative to the transpiled JS files.