Add Material Icons link and update version in the CDN example on Getting Started page

[pgoldtho]

The getting started CDN example is currently broken. The links to version 2.2.0 return a 404 and is missing a link to download material icons. Here's what I used to get it working:

    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@materializecss/materialize@2.2.1/dist/css/materialize.min.css">
    <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
    <script src="https://cdn.jsdelivr.net/npm/@materializecss/materialize@2.2.1/dist/js/materialize.min.js"></script>