Add 3d rotations

[paulnovo]

This adds 3D support to the Rotate transformation, and introduces RotateX, RotateY, and RotateZ for 3D rotations around the x, y, and z axes.

PR Checklist

• [x] Tests are added
• [x] Documentation, if applicable

[CarloLucibello]

Thanks! Could you add to the documentation in doc/src/transforms.md and docs/src/ref.md?

[paulnovo]

Thanks! Could you add to the documentation in doc/src/transforms.md and docs/src/ref.md?

Hi @CarloLucibello, thanks for taking a look. I just pushed two commits. The first commit is probably what you were looking for, just adding the documentation to ref.md. In a second commit, I went much further with a bit of reorganization, but maybe not what you wanted. I can pull this commit out into a separate PR if that makes more sense.

[CarloLucibello]

I like the reorganization! still something to do or we can merge?

[paulnovo]

@CarloLucibello I am all done with this, you can merge.