Refactors: Moves linear algebra to new directory

Moves linear algebra headers to a new subdirectory to improve project structure.

Updates includes to reflect the directory change.
Adds vcpkg to the tracked repositories.

include/omath/engines/unity_engine/constants.hpp

@@ -4,9 +4,9 @@
 
 #pragma once
 
+#include "omath/linear_algebra/mat.hpp"
+#include "omath/linear_algebra/vector3.hpp"
 #include <omath/angle.hpp>
-#include <omath/mat.hpp>
-#include <omath/vector3.hpp>
 #include <omath/view_angles.hpp>
 
 namespace omath::unity_engine