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)_.
expect(markInfo.UserProperties).toEqual(false);
      expect(markInfo.Suspects).toEqual(false);
    });
    it("gets data", async function () {
      const data = await pdfDocument.getData();
      expect(data instanceof Uint8Array).toEqual(true);
      expect(data.length).toEqual(basicApiFileLength);
    });
    it("gets download info", async function () {
      const downloadInfo = await pdfDocument.getDownloadInfo();
      expect(downloadInfo).toEqual({ length: basicApiFileLength });
    });
    it("gets document stats", async function () {
      const stats = pdfDocument.stats;
      expect(stats).toEqual(null);
    });
    it("cleans up document resources", async function () {
      await pdfDocument.cleanup();
      expect(true).toEqual(true);
    });
    it("checks that fingerprints are unique", async function () {
      const loadingTask1 = getDocument(
        buildGetDocumentParams("issue4436r.pdf")
      );
      const loant(buildGetDocumentParams("issue4575.pdf"));
      const data = await Promise.all([
        loadingTask1.promise,
        loadingTask2.promise,
      ]);
      const fingerprints1 = data[0].fingerprints;