index modification

public/index.html

@@ -14,6 +14,11 @@
     </div>
 
     <h1>Hello World!</h1>
+    <h2>Hello World!</h2>
+    <h3>Hello World!</h3>
+    <h4>Hello World!</h4>
+    <h5>Hello World!</h5>
+    <h6>Hello World!</h6>
 
     <p>
       This is a simple plain-HTML website on GitLab Pages, without any fancy static site generator.