Rename JSON key resolver to better expose what it's doing

osu.Game/IO/Serialization/SnakeCaseKeyContractResolver.cs

@@ -0,0 +1,16 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using Humanizer;
+using Newtonsoft.Json.Serialization;
+
+namespace osu.Game.IO.Serialization
+{
+    public class SnakeCaseKeyContractResolver : DefaultContractResolver
+    {
+        protected override string ResolvePropertyName(string propertyName)
+        {
+            return propertyName.Underscore();
+        }
+    }
+}