add SoundSettings

Assets/Prefabs/Settings.prefab

@@ -15,6 +15,7 @@ GameObject:
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   m_Layer: 0
   m_Name: Settings
   m_TagString: Untagged
@@ -108,3 +109,16 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: 409653cfe36614ceab3cbfbf9ed04fce, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
+--- !u!114 &8776297466843115784
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+  m_Script: {fileID: 11500000, guid: 0c095ea8fdb7ab740a96b2a7ae1cc4b2, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: 
+  defaultSoundVolume: 0.5

Assets/Scripts/Settings/SoundSettings.cs

@@ -0,0 +1,24 @@
+using SanAndreasUnity.UI;
+using UnityEngine;
+
+namespace SanAndreasUnity.Settings
+{
+    public class SoundSettings : MonoBehaviour
+    {
+        [Range(0f, 1f)] public float defaultSoundVolume = 0.5f;
+
+        OptionsWindow.FloatInput m_soundVolume = new OptionsWindow.FloatInput ("Sound volume", 0, 1) {
+            getValue = () => AudioListener.volume,
+            setValue = (value) => { AudioListener.volume = value; },
+            persistType = OptionsWindow.InputPersistType.OnStart
+        };
+
+        private void Awake()
+        {
+            // apply default value
+            AudioListener.volume = this.defaultSoundVolume;
+
+            OptionsWindow.RegisterInputs ("SOUND", m_soundVolume);
+        }
+    }
+}

Assets/Scripts/Settings/SoundSettings.cs.meta

@@ -0,0 +1,11 @@
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