[Math][Matrix] Support both LookAtRh and LookAtLH or, at least, add the coordinate system in comments or in readme

# Summary of feature
Add support for both coordinate system for LookAt matrix. Like it is in Stride 3D Engine
https://github.com/stride3d/stride/blob/master/sources/core/Stride.Core.Mathematics/Matrix.cs

Or add some comments on the LookAt function to explicitely write the coordinate system. Or/And add it in the readme of the project

# Comments

# Does this have a proposal?
Check the documentation/proposals folder. If it doesn't have one, you may need to create one if you're making **massive breaking changes**.