Macro transform 

macro_rules! transform {
    (pos: $pos:expr, rot: $rot:expr, scale: $scale:expr) => { ... };
    (x: $x:expr, y: $y:expr) => { ... };
    (pos: $pos:expr) => { ... };
}

create a Transform from components.

example

use lunar_math::{transform, Vec2};

let t = transform!(pos: Vec2::new(10.0, 20.0), rot: 0.5, scale: Vec2::ONE);