Linear interpolation for matrix

[Dimach]

I added method for matrix which would be useful.

[httpdigest]

Can you name a use-case in which linearly componentwise interpolation of the matrix elements could be useful? I currently only see that an Eigenvalue decomposition with a linear interpolation of translation and scale and a spherical interpolation of the rotation components could be useful.

[Dimach]

I use that for interpolate key frames in my skeletal animation library. Spherical interpolation of rotation component not needed in this case because key frames fairly frequently and vector length change
insensibly.

[httpdigest]

Hey @Dimach, I finally added your proposed Matrix.lerp() methods to all matrices, including the 4x3 ones. Additionally, I chose a faster interpolation method and added a minor JavaDoc fix.
Thanks for suggestion and providing the initial JavaDoc/implementation!