Add setting for changing mod select hotkey style

osu.Game/Overlays/Mods/Input/ModSelectHotkeyStyle.cs

@@ -0,0 +1,27 @@
+// 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 osu.Game.Rulesets.Mods;
+
+namespace osu.Game.Overlays.Mods.Input
+{
+    /// <summary>
+    /// The style of hotkey handling to use on the mod select screen.
+    /// </summary>
+    public enum ModSelectHotkeyStyle
+    {
+        /// <summary>
+        /// Each letter row on the keyboard controls one of the three first <see cref="ModColumn"/>s.
+        /// Individual letters in a row trigger the mods in a sequential fashion.
+        /// Uses <see cref="SequentialModHotkeyHandler"/>.
+        /// </summary>
+        Sequential,
+
+        /// <summary>
+        /// Matches keybindings from stable 1:1.
+        /// One keybinding can toggle between what used to be <see cref="MultiMod"/>s on stable,
+        /// and some mods in a column may not have any hotkeys at all.
+        /// </summary>
+        Classic
+    }
+}