const installButton = document.getElementById('install-app');
    let beforeInstallPromptEvent
    window.addEventListener("beforeinstallprompt", function(e) {
        e.preventDefault();
        beforeInstallPromptEvent = e
        installButton.removeClass = 'is-hidden';  BURDA CLASSI SiLMEYE
        installButton.addEventListener("click", function() {
            e.prompt();
        });
        installButton.addClass = "is-hidden"; BURADADA EKLEMEYE ÇALIŞTIM
    });
    installButton.addEventListener("click", function() {
        beforeInstallPromptEvent.prompt();
    });