There are two recommended methods to include external JavaScript packages in your Embeddable:
  1. Direct HTML Inclusion (Recommended): Add the script tag directly to the HTML of the page where you’re embedding your Embeddable, alongside the Embeddables embed code.
  2. JavaScript Action Method: Load the package programmatically through an Action that triggers when the Embeddable loads.
If you choose #2, here’s sample code for inserting a <link> tag: 
// All Actions must contain a function called output()
function output() {
  // Add the link tag
  loadStylesheet("<URL>");
}

// Helper function to add a link tag to the head of the page
function loadStylesheet(href) {
  const link = document.createElement("link");
  link.rel = "stylesheet";
  link.href = href;
  document.head.appendChild(link);
}