Add C# Tips to 3d tutorial game

getting_started/first_3d_game/06.jump_and_squash.rst

@@ -269,6 +269,8 @@ With this code, if no collisions occurred on a given frame, the loop won't run.
             KinematicCollision3D collision = GetSlideCollision(index);
 
             // If the collision is with a mob.
+            // With C# we leverage typing and pattern-matching
+            // instead of checking for the group we created.
             if (collision.GetCollider() is Mob mob)
             {
                 // We check that we are hitting it from above.
@@ -344,6 +346,10 @@ destroy the mob.
         QueueFree();
     }
 
+.. note::
+
+    When using C#, Godot will create the appropriate events automatically for all Signals ending with `EventHandler`, see :ref:`C# Signals <doc_c_sharp_signals>`.
+
 We will use the signal to add points to the score in the next lesson.
 
 With that, you should be able to kill monsters by jumping on them. You can press