You can use custom javascript to add this snippet. Don't know how to do it? Checkout
// Load Zendesk Widget Dynamically
function loadZendeskWidget() {
var script = document.createElement('script');
script.type = 'text/javascript';
script.id = 'ze-snippet';
script.async = true;
script.src = 'https://static.zdassets.com/ekr/snippet.js?key=YOURKEYGOESHERE';
document.getElementsByTagName('head')[0].appendChild(script);
};
document.body.onload = function () {
loadZendeskWidget();
};
Don't forget to replace YOURKEYGOESHERE with your Zendesk key.
If you want to learn more about adding this script dynamically, you can checkout this post: Dynamically Script Loading Zendesk Widget