Use the smooth scrolling behavior

src/main/resources/index.html

@@ -9,6 +9,9 @@
     <link href="https://fonts.googleapis.com/css2?family=Noto+Sans&display=swap" rel="stylesheet">
     <title>www.username404.fr</title>
     <style>
+        html {
+            scroll-behavior: smooth;
+        }
         body {
             text-align: center;
             text-decoration-color: #868e96;