Add oblique animation option

[nebiyuelias1]

I'm submitting a ... (check one with "x")

• feature request

Current behavior
Currently, the only animations available are pulse and progress.

Expected behavior
But, I want to also have a new kind of animation (I call it oblique, might not be a good name) that moves the gradient from the top left to the bottom right.

Well, I kind of want to have this kind of animation for one of my projects.