improve accessibility

app/views/start_form/private.html.erb

@@ -2,7 +2,7 @@
 <% I18n.with_locale(@template.account.locale) do %>
   <% content_for(:html_description, t('share_link_is_currently_disabled')) %>
 <% end %>
-<div class="max-w-md space-y-6 mx-auto px-2 mt-12 mb-4">
+<main class="max-w-md space-y-6 mx-auto px-2 mt-12 mb-4">
   <div class="text-center w-full space-y-6">
     <%= render 'banner' %>
     <p class="text-xl font-semibold text-center">
@@ -27,5 +27,5 @@
       <%= button_to button_title(title: t('enable_shared_link'), icon: svg_icon('lock_open', class: 'w-6 h-6')), template_share_link_path(@template), params: { template: { shared_link: true }, redir: start_form_path(slug: @template.slug) }, method: :post, class: 'white-button w-full' %>
     </toggle-submit>
   <% end %>
-</div>
+</main>
 <%= render 'shared/attribution', link_path: '/start', account: @template.account %>