Implement missing 3D Affine Transforms in the Struct API

[FrostKiwi]

This PR solves #316 by adding three 3D Affine Transform functions, which were previously missing from the struct api:

CGLM_INLINE mat4s glms_mul(mat4 m1, mat4 m2);
CGLM_INLINE mat4s glms_mul_rot(mat4 m1, mat4 m2);
CGLM_INLINE mat4s glms_inv_tr();

[recp]

@FrostKiwi many thanks for bringing missing features to strut API. One thing, we need to add this new file to build files.

[FrostKiwi]

@FrostKiwi many thanks for bringing missing features to strut API. One thing, we need to add this new file to build files.

Added to the Makefile via c4d4c48 and to the Visual Studio project files via a7cda7f. I put it into separate commits, for a convenient revert, in case I was not supposed do one of them.

[recp]

@FrostKiwi thanks for your contributions, the PR is merged 🚀