Split audio types into separate files

Raylib-cs/types/Sound.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Raylib_cs;
+
+/// <summary>
+/// Sound source type
+/// </summary>
+[StructLayout(LayoutKind.Sequential)]
+public partial struct Sound
+{
+    /// <summary>
+    /// Audio stream
+    /// </summary>
+    public AudioStream Stream;
+
+    /// <summary>
+    /// Total number of frames (considering channels)
+    /// </summary>
+    public uint FrameCount;
+}