Add joystick/gamepad deadzone setting

Also splits joystick/gamepad into a new sub-section.

osu.Game/Localisation/JoystickSettingsStrings.cs

@@ -0,0 +1,21 @@
+using osu.Framework.Localisation;
+
+namespace osu.Game.Localisation
+{
+    public static class JoystickSettingsStrings
+    {
+        private const string prefix = @"osu.Game.Resources.Localisation.JoystickSettings";
+
+        /// <summary>
+        /// "Joystick / Gamepad"
+        /// </summary>
+        public static LocalisableString JoystickGamepad => new TranslatableString(getKey(@"joystick_gamepad"), @"Joystick / Gamepad");
+
+        /// <summary>
+        /// "Deadzone Threshold"
+        /// </summary>
+        public static LocalisableString DeadzoneThreshold => new TranslatableString(getKey(@"deadzone_threshold"), @"Deadzone Threshold");
+
+        private static string getKey(string key) => $@"{prefix}:{key}";
+    }
+}

osu.Game/Overlays/Settings/Sections/Input/JoystickSettings.cs

@@ -0,0 +1,62 @@
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Input.Handlers.Joystick;
+using osu.Framework.Localisation;
+using osu.Game.Graphics.UserInterface;
+using osu.Game.Localisation;
+
+namespace osu.Game.Overlays.Settings.Sections.Input
+{
+    public class JoystickSettings : SettingsSubsection
+    {
+        private readonly JoystickHandler joystickHandler;
+           
+            protected override LocalisableString Header => JoystickSettingsStrings.JoystickGamepad;
+            private readonly BindableNumber<float> deadzoneThreshold = new BindableNumber<float>();
+            private readonly Bindable<bool> enabled = new BindableBool(true);
+            public JoystickSettings(JoystickHandler joystickHandler)
+            {
+                this.joystickHandler = joystickHandler;
+            }
+            [BackgroundDependencyLoader]
+            private void load()
+            {
+                Children = new Drawable[]
+                {
+                    new SettingsCheckbox
+                    {
+                        LabelText = CommonStrings.Enabled,
+                        Current = enabled
+                    },
+                    new DeadzoneSetting
+                    {
+                        LabelText = JoystickSettingsStrings.DeadzoneThreshold,
+                        Current = deadzoneThreshold
+                    },
+                };
+            }
+
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+                enabled.BindTo(joystickHandler.Enabled);
+                deadzoneThreshold.BindTo(joystickHandler.DeadzoneThreshold);
+                enabled.BindValueChanged(e => deadzoneThreshold.Disabled = !e.NewValue, true);
+            }
+
+            private class DeadzoneSetting : SettingsSlider<float, DeadzoneSlider>
+            {
+                public DeadzoneSetting()
+                {
+                    KeyboardStep = 0.005f;
+                    TransferValueOnCommit = true;
+                }
+            }
+            
+            private class DeadzoneSlider : OsuSliderBar<float>
+            {
+                public override LocalisableString TooltipText => Current.Disabled ? "" : base.TooltipText;
+            }
+    }
+}

osu.Game/Overlays/Settings/Sections/InputSection.cs

@@ -68,7 +68,10 @@ namespace osu.Game.Overlays.Settings.Sections
                     break;
 
                 // whitelist the handlers which should be displayed to avoid any weird cases of users touching settings they shouldn't.
-                case JoystickHandler _:
+                case JoystickHandler jh:
+                    section = new JoystickSettings(jh);
+                    break;
+
                 case MidiHandler _:
                     section = new HandlerSection(handler);
                     break;