refactor: updated screenshot.js to use dynamic module imports

src/toolbar/preview/screenshot.js

@@ -1,25 +1,11 @@
-let html2canvasPromise;
-
 const screenshot = async () => {
   document.getElementById('prismic-toolbar-v2').setAttribute('data-html2canvas-ignore', true);
-  if (!html2canvasPromise) html2canvasPromise = script('https://html2canvas.hertzen.com/dist/html2canvas.min.js');
-  await html2canvasPromise;
-
-  const canvas = await window.html2canvas(document.body, {
-    logging: false,
-    width: '100%',
-    height: window.innerHeight,
-  });
-  return new Promise(resolve => canvas.toBlob(resolve, 'image/jpeg', 0.6));
-};
 
-function script(src) {
-  return new Promise(resolve => {
-    const el = document.createElement('script');
-    el.src = src;
-    document.head.appendChild(el);
-    el.addEventListener('load', () => resolve(el));
-  });
+  const options = { logging: false, width: '100%', height: window.innerHeight };
+
+  return import('https://html2canvas.hertzen.com/dist/html2canvas.esm.js')
+  .then(html2canvas => html2canvas(document.body, options))
+  .then(canvas => new Promise(resolve => canvas.toBlob(resolve, 'image/jpeg', 0.6)));
 }
 
 export default screenshot;