reset = (end, textLayer) => {
      if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
        textLayer.append(end);
        end.style.width = "";
        end.style.height = "";
      }
      textLayer.classList.remove("selecting");
    }
Improves text selection by adding an additional div where the mouse was
clicked. This reduces flickering of the content if the mouse is slowly
dragged up or down.