Tutorials (schueltke): repaired link

docs/index.md

@@ -41,7 +41,7 @@ Learn how to set it up & install the prerequisites.
 
 Design your first aircraft.
 
-[:octicons-arrow-right-24: Tutorials](tutorials/standalone.mp4)
+[:octicons-arrow-right-24: Tutorials](tutorials/changing-design-specifications.md)
 </div>
 
 <div class="grid-item card" markdown="1">