add indirect draw command struct

src/Refresh.cs

@@ -367,6 +367,15 @@ namespace RefreshCS
 			public uint level;
 		}
 
+		[StructLayout(LayoutKind.Sequential)]
+		public struct IndirectDrawCommand
+		{
+			public uint vertexCount;
+			public uint instanceCount;
+			public uint firstVertex;
+			public uint firstInstance;
+		}
+
 		[StructLayout(LayoutKind.Sequential)]
 		public struct SamplerStateCreateInfo
 		{