Hello!

Let me know if i should have opened this issue on the [pdfjs-dist](https://github.com/mozilla/pdfjs-dist) repo but I though here would fit.

I'm using pdfjs-dist and I'm in need of some more types to be exported. I have no idea how the types end up in the dist-repo but would love to open a PR if only someone could point me in the right direction 😃 Since I was using an older version of pdfjs-dist I realize the only type I need that's not in the type defs in the latest release are _PageViewport_ from _[display/display_utils](https://github.com/mozilla/pdf.js/blob/master/src/display/display_utils.js#L153)_.
// A PDF using the Arial font.
    const pdf3 = buildGetDocumen
    const loadingTasks = [];
    // Render the first page of the given PDF file.
    // Fulfills  the PDF.
    async function renderPDF(filename) {
      const loadingTask = getDocument(filename);
      loadingTasks.push(loadingTask);
      const pdf = await loadingTask.promise;
      const page = await pdf.getPage(1);
      const viewport = page.getViewport({ scale: 1.2 });
      const canvasAndCtx = CanvasFactory.create(
        viewport.width,
        viewport.height
      );
      const renderTask = page.render({
        canvasContext: canvasAndCtx.context,
        canvasFactory: CanvasFactory,
        viewport,
      });
      await renderTask.promise;
      const data = canvasAndCtx.canvas.toDataURL();
      CanvasFactory.destroy(canvasAndCtx);
      return data;
    }
    afterEach(async function () {
      // Issue 6205 reported an issue with font rendering, so clear the loaded
      // fonts so that we can see whether loading PDFs in parallel does not
      // cause any issues with the rendered fonts.
      const destrongTask) {