Revert 2d tutorial link

Author: SimonDarksideJ

articles/tutorials/index.md

@@ -13,7 +13,7 @@ description: Tutorials provided by MonoGame community members.
         <div class="col-12 col-lg-4 mb-5">
             <div class="mg-card mg-box-shadow h-100">
                 <a target="_self"
-                    href="building_2d_games/Index.html"
+                    href="building_2d_games/Index.md"
                     class="mg-no-link">
                     <div class="mg-card-body d-flex flex-column h-100">
                         <div class="mg-card-title"><i class="bi bi-files"></i> 2D Getting started tutorial</div>