Do yourself a favour and reference to the exact version of Ionic framework you have developed against (if you haven’t already). If you use the general one, once the CDN gets update with the new framework (Ionic 6 is arriving), then you WILL have things breaking in your site/app
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<script nomodule src="https://cdn.jsdelivr.net/npm/@ionic/core@5.4.0/dist/ionic/ionic.js"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@ionic/core@5.4.0/css/ionic.bundle.css" />