Adding version popup in Anki Deck description

versionPopup.html

<style>
.popup {
  position: relative;
  display: inline-block;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}
.popup .popuptext {
  visibility: hidden;
  width: 160px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 8px 0;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;
  margin-left: -80px;
}
.popup .show {
  visibility: visible;
  -webkit-animation: fadeIn 1s;
  animation: fadeIn 1s;
}
.btn {
  height:25px;
  width:45px;
  padding:2px;
  background-color: #e53935;
  border: none;
  border-radius: 3px; 
  color: white;
  outline:none;
}
.btn:hover {
  background-color: #f44336;
}
</style>
<script>
var deckVersion = "1.2";  // version come with deck

var xhttp = new XMLHttpRequest();
var obj;
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
       obj = JSON.parse(this.responseText);
       //console.log(obj);
       if (obj['version'] > deckVersion) {    // comparing deck version with version inside json
        console.log('update available');
        var popup = document.getElementById("versionPopup");
        popup.classList.toggle("show");
        }
    }
};
xhttp.open("GET", "https://cdn.jsdelivr.net/gh/infinyte7/Write-Kanji@master/Versions/version.json", true);  // version file on GitHub
xhttp.send();
</script>
<center>
<a class="popup" href="https://github.com/infinyte7/Write-Kanji/releases"><span class="popuptext" id="versionPopup">Update Available <button class="btn">update</button></span></a>
</center>