Aww yeah, appendGrid for Bootstrap 4 is coming!
Download
Please download the js and css file at appendGrid's GitHub Repository. And then copy and reference them in your website.
Reference files
Here is an example that included all files required for appendGrid.
<html>
<head>
<!--jQuery UI Core, Widget and Button components are mandatory-->
<link href="jquery-ui-1.12.1.css" rel="stylesheet"/>
<link href="jquery.appendGrid-x.x.x.css" rel="stylesheet"/>
<script type="text/javascript" src="jquery-1.12.4.js"></script>
<script type="text/javascript" src="jquery-ui-1.12.1.js"></script>
<script type="text/javascript" src="jquery.appendGrid-x.x.x.js"></script>
<script type="text/javascript">
    $(function () {
        $('#tblAppendGrid').appendGrid({ /* Initial parameters */ });
    });
</script>
</head>
<body>
    <table id="tblAppendGrid"></table>
</body>
</html>