Adding a function to angle to reduce it to the princlple domain [0, 2𝜋) radians

[tedgin]

When working with angles, it is often useful to convert their values to the principle domain [0, 2𝜋) radians. For examples, an angle of 540 degrees would be converted to 180 degrees, and an angle of -90 degrees would be converted to 270 degrees. This is different from the existing Angle::fract::<revolution>(), which returns the fractional part of a revolution. fract::<revolution>() maps -90 degrees to -90 degree.

Would a function like this make sense in uom? If so, I'm willing to submit a PR.