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(opListAnnotEnableStorage.fnArray.length).toBeGreaterThan(170);
      expect(opListAnnotEnableStorage.argsArray.length).toBeGreaterThan(170);
      expect(opListAnnotEnableStorage.lastChunk).toEqual(true);
      // Sanity check to ensure that the `annotationMode` is correctly applied.
      expect(opListAnnotDisable.fnArray.length).toBeLessThan(
        opListAnnotEnableForms.fnArray.length
      );
      expect(opListAnnotEnableForms.fnArray.length).toBeLessThan(
        opListAnnotEnable.fnArray.length
      );
      expect(opListAnnotEnable.fnArray.length).toBeLessThan(
        opListAnnotEnableStorage.fnArray.length
      );
      await loadingTask.destroy();
    });
    it("gets operatorList, with page resources containing corrupt /CCITTFaxDecode data", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("poppler-90-0-fuzzed.pdf")
      );
      expect(loadingTask instanceof PDFDocumentLoadingTask).toEqual(true);
      const pdfDoc = await loadingTask.promise;
      expect(pdfDoc.numPages).toEqual(16);
      const pdfPage = await pdfDoc.getPage(6);
      expect(pdfPage instanceof PDFPageProxy).toEqual(true);
      const opList = await pdfPage.getOperatorList();
      expect(opList.fnArray.length).toBeGreaterThan(25);
      expect(opList.argsArray.length).toBeGreaterThan(25);
      expect(opList.lastChunk).toEqual(true);
      await loadingTask.destroy();
    });