Investigate adding a gsk::ColorStopBuilder

[bilelmoussaoui]

So instead of doing

append_conic_gradient(...., &[
    gsk::ColorStop::new(0.0, gdk::RGBA::white()),
    gsk::ColorStop::new(0.333, gdk::RGBA::from_str("#FF0000").unwrap()),
    gsk::ColorStop::new(0.667, gdk::RGBA::from_str("#0000FF").unwrap()),
    gsk::ColorStop::new(1.0, gdk::RGBA::from_str("#FF0000").unwrap()),
]);

You could do something like

append_conic_gradient(&..., 
    &gsk::ColorStop::builder().
        .stop(0.0, gdk::RGBA::white())
        .stop(0.333, gdk::RGBA::from_str("FF0000").unwrap())
        .stop(0.667, gdk::RGBA::from_str("#0000FF").unwrap())
        .stop(1.0, gdk::RGBA::from_str("#FF0000").unwrap())
        .build()
);