feat(15): index placeholder for the form

to be htmx'ed into getting appropriate step for the session

15-multi-step-form/src/main/resources/templates/step1.html

@@ -35,7 +35,7 @@
       </p>
     <![endif]-->
 
-    <article
+    <form
       class="flex flex-col items-center w-screen h-screen md:grid md:items-start md:p-5 md:bg-white md:rounded-2xl md:grid-cols-[auto_1fr] md:w-desktop-form md:h-desktop-form md:drop-shadow-2xl"
       id="form-step"
     >
@@ -137,7 +137,7 @@
           >Next Step</a
         >
       </section>
-    </article>
+    </form>
     <div class="fixed inset-x-0 bottom-0 attribution">
       Challenge by
       <a href="https://www.frontendmentor.io?ref=challenge" target="_blank"