Add with_x , with_y, to Vec3

[silvestrpredko]

I would to discuss the possibility of adding additional API to Vec3.

Something like that:

#[must_use]
#[inline]
pub fn with_z(mut self, z: f32) -> Self {
    self.z = z;
    self
}

For 2d games a lot of time you need to update only one property from Vec3. It would be nice to have this out of the box. What do you think? I plan to add this API but at first want to discuss if it will be accepted, and I just don't waste my time.

Thanks

[bitshifter]

Seems reasonable, I've created an issue for this #490