Add sleep function for panorama

[GniLudio]

The sleep functions let's you simplify asynchronous sequences:

async function foo() {
    $.Msg("Do something");
    await sleep(3);
    $.Msg("Do something else");
    await sleep(1);
    $.Msg("Do another thing");
    await sleep(0.1);
    $.Msg("Do even more things");
    await sleep(1);
    $.Msg("End with something");
}

instead of

function foo() {
    $.Msg("Do something");
    $.Schedule(3, () => {
        $.Msg("Do something else");
        $.Schedule(1, () => {
            $.Msg("Do another thing");
            $.Schedule(0.1, () => {
                $.Msg("Do even more things");
                $.Schedule(1, () => {
                    $.Msg("End with something");
                });
            });
        });
    });
}