extract shader types to module

Sources/Voxelotl/shader.metal

@@ -1,25 +1,4 @@
-#ifndef SHADERTYPES_H
-#define SHADERTYPES_H
-
-#ifdef __METAL_VERSION__
-# define NS_ENUM(TYPE, NAME) enum NAME : TYPE NAME; enum NAME : TYPE
-# define NSInteger metal::int32_t
-#else
-# import <Foundation/Foundation.h>
-#endif
-
-#include <simd/simd.h>
-
-typedef NS_ENUM(NSInteger, ShaderInputIdx) {
-  ShaderInputIdxVertices = 0
-};
-
-typedef struct {
-  vector_float4 position;
-  vector_float4 color;
-} ShaderVertex;
-
-#endif//SHADERTYPES_H
+#include "shadertypes.h"
 
 #include <metal_stdlib>