HIFIS for you:

`fa-lightbulb` -> `fa-user-plus`

_includes/frontpage/title-content.html

@@ -11,7 +11,7 @@
             <i class="fas fa-laptop-code"></i> Helmholtz Software
         </a>
         <a href="{{ '/you-and-hifis' | relative_url }}" class="btn btn-light btn-lg text-dark">
-            <i class="fas fa-lightbulb"></i> HIFIS for you
+            <i class="fas fa-user-plus"></i> HIFIS for you
         </a>
         <a href="{{ '/contact' | relative_url }}" class="btn btn-light btn-lg text-dark">
             <i class="fas fa-question"></i> Support + Contact