Check for status code change periodically. Designed to be pasted in Chrome Dev Tools to bypass any CORS issues.

checkStatus.js

function check (DELAY_MINUTE = 1, RESPONSE_CODE = 200) {
    var req = new XMLHttpRequest()
    req.addEventListener('load', onLoad)
    function open () {
        req.open('HEAD', location.href, true)
        req.send()
    }
    function onLoad () {
        req.status === RESPONSE_CODE ? notify() : setTimeout(open, DELAY_MINUTE * 60 * 1000)
    }
    function notify() {
        const str = `Yay! ${location.href} is available!`
        Notification.permission === 'granted' ? new Notification(str, { sticky: true }) : alert(str)
    }
    Notification.requestPermission((permission) => {
        open()
    })
    window.onbeforeunload = function(e) {
        return e.returnValue = 'Work in progress, sure you wanna quit?'
    }
}