Add 404 and 500 page

templates/404.html

@@ -0,0 +1,8 @@
+{% extends "base.html" %}
+{% block main %}
+    <div class="mt-4 text-center">
+        <h1>Oops ! This page does not exist</h1>
+        <h2 class="fst-italic">404 NOT FOUND</h2>
+        <a href="/" class="mt-3 btn btn-info">Back to home</a>
+    </div>
+{% endblock %}