make vec4 and matrix types internal

src/twn_types_c.h

@@ -0,0 +1,19 @@
+#ifndef TWN_TYPES_C_H
+#define TWN_TYPES_C_H
+
+#include <stdint.h>
+
+typedef struct Vec4 {
+    float x;
+    float y;
+    float z;
+    float w;
+} Vec4;
+
+
+typedef struct Matrix4 {
+    Vec4 row[4];
+} Matrix4;
+
+
+#endif