cam: extend frustum's far distance helper (#71)

* this will help to implement zoom easily

src/cam.c

@@ -88,6 +88,12 @@ glmc_perspective(float fovy,
                   dest);
 }
 
+CGLM_EXPORT
+void
+glmc_persp_move_far(mat4 proj, float deltaFar) {
+  glm_persp_move_far(proj, deltaFar);
+}
+
 CGLM_EXPORT
 void
 glmc_perspective_default(float aspect, mat4 dest) {