add function, type and macros in header to top of header

include/cglm-affine-mat.h

@@ -5,6 +5,12 @@
  * Full license can be found in the LICENSE file
  */
 
+/*
+ Functions:
+   CGLM_INLINE void glm_mul(mat4 m1, mat4 m2, mat4 dest);
+   CGLM_INLINE void glm_inv_tr(mat4 mat);
+ */
+
 #ifndef cglm_affine_mat_h
 #define cglm_affine_mat_h