user page: link representative h-card warning to indiewebify.me

for #305

templates/user.html

@@ -16,7 +16,7 @@
 <div class="row promo warning">
 <p>Your site doesn't have a
   <a href="https://indieweb.org/representative_h-card">representative h-card</a>.
-  <a href="https://indieweb.org/h-card#How">Please add one!</a>
+  <a href="https://indiewebify.me/validate-h-card/?url=https://{{ domain }}">Check it here!</a>
 </p>
 </div>
 {% endif %}