Fix 404.html homepage link to use / instead of site.baseurl

Co-authored-by: calcode <8709992+calcode@users.noreply.github.com>

Author: Copilot

404.html

@@ -6,5 +6,5 @@
 
 <div class="page">
   <h1 class="page-title">Page not found (404)</h1>
-  <p class="lead">Uh oh. Something doesn't seem right here! <a href="{{ site.baseurl }}">Head back to the homepage</a>.</p>
+  <p class="lead">Uh oh. Something doesn't seem right here! <a href="/">Head back to the homepage</a>.</p>
 </div>