add subscribe button

site link to make subscribe button
https://developers.google.com/youtube/youtube_subscribe_button

also code hare
<script src="https://apis.google.com/js/platform.js"></script>

<script>
  function onYtEvent(payload) {
    if (payload.eventType == 'subscribe') {
      // Add code to handle subscribe event.
    } else if (payload.eventType == 'unsubscribe') {
      // Add code to handle unsubscribe event.
    }
    if (window.console) { // for debugging only
      window.console.log('YT event: ', payload);
    }
  }
</script>

<div class="g-ytsubscribe" data-channelid="UCYtjjCdSrMAgPALIq929lNA" data-layout="full" data-count="default" data-onytevent="onYtEvent"></div>