Support versions of PDF.js >= v3.2.146

This release includes https://github.com/mozilla/pdf.js/pull/15722 which
changed the property that stores the root of the text layer.

The tests mocks still use the old `textLayerDiv` name because that is
what is used in the PDF.js release that we currently ship.

src/annotator/anchoring/pdf.js

@@ -314,7 +314,12 @@ async function anchorByPosition(pageIndex, start, end) {
     // `getPageTextContent` and the text layer content. Any other differences
     // will cause mis-anchoring.
 
-    const root = page.textLayer.textLayerDiv;
+    const root = page.textLayer.textLayerDiv ?? page.textLayer.div;
+    if (!root) {
+      /* istanbul ignore next */
+      throw new Error('Unable to find PDF.js text layer root');
+    }
+
     const textLayerStr = /** @type {string} */ (root.textContent);
 
     const [textLayerStart, textLayerEnd] = translateOffsets(

src/types/pdfjs.js

@@ -146,7 +146,8 @@
 /**
  * @typedef TextLayer
  * @prop {boolean} renderingDone
- * @prop {HTMLElement} textLayerDiv
+ * @prop {HTMLElement} [div] - New name for root element of text layer in PDF.js >= v3.2.146
+ * @prop {HTMLElement} [textLayerDiv] - Old name for root element of text layer
  */
 
 export {};