Add 404 page

content/pages/404.md

@@ -1,7 +1,7 @@
 Title: Erreur 404
-Status: hidden 
+Status: hidden
 Save_as: 404.html
 slug: 404
 url: 404.html
 
-![404 Not Found Cat](https://http.cat/404 "404 Not Found Cat")
+![404 Not Found](../assets/404.png)