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)_.
const urlObj = new URL(
        TEST_PDFS_PATH + basicApiFileName,
        window.location
      );
      const loadingTask = getDocument(urlObj);
      expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
      const pdfDocument = await loadingTask.promise;
      expect(urlObj instanceof URL).toEqual(true);
      expect(pdfDocument instanceof PDFDocumentProxy).toEqual(true);
      expect(pdfDocument.numPages).toEqual(3);
      await loadingTask.destroy();
    });
    it("creates pdf doc from URL", async function () {
      const loadingTask = getDocument(basicApiGetDocumentParams);
      expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
      const progressReportedCapability = createPromiseCapability();
      
      
      loadingTask.onProgress = function (progressData) {
        if (!progressReportedCapability.settled) {
          progressReportedCapability.resolve(progressData);
        }
      };
      const data = await Promise.all([
        progressReportedCapability.promise,
        loadingTask.promise,
      ]);
      expect(data[0].loaded / data[0].total >= 0).toEqual(true);
      expect(data[1] instanceof PDFDocumentProxy).toEqual(true);
      expect(loadingTask).toEqual(data[1].loadingTask);