Change CollisionEventArgs settter to init require (#978)

Closes #977

source/MonoGame.Extended/Collisions/CollisionEventArgs.cs

@@ -12,7 +12,7 @@ namespace MonoGame.Extended.Collisions
         /// <summary>
         /// Gets the object being collided with.
         /// </summary>
-        public ICollisionActor Other { get; internal set; }
+        public required ICollisionActor Other { get; init; }
 
         /// <summary>
         /// Gets a vector representing the overlap between the two objects.
@@ -21,6 +21,6 @@ namespace MonoGame.Extended.Collisions
         /// This vector starts at the edge of <see cref="Other"/> and ends at
         /// the Actor's location.
         /// </remarks>
-        public Vector2 PenetrationVector { get; internal set; }
+        public required Vector2 PenetrationVector { get; init; }
     }
-}
+}