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 loadingTask = getDocument(buildGetDocumentParams("issue13201.pdf"));
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const { items } = await pdfPage.getTextContent();
      const text = mergeText(items);
      expect(
        text.includes(
          "Abstract. A purely peer-to-peer version of electronic cash would allow online"
        )
      ).toEqual(true);
      expect(
        text.includes(
          "avoid mediating disputes. The cost of mediation increases transaction costs, limiting the"
        )
      ).toEqual(true);
      expect(
        text.includes(
          "system is secure as long as honest nodes collectively control more CPU power than any"
        )
      ).toEqual(true);
      await loadingTask.destroy();
    });
    it("gets text content, with no spaces between letters of words (issue 11913)", async function () {
      const loadingTask = getDocument(buildGetDocumentParams("issue11913.pdf"));
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const { items } = await pdfPage.getTextContent();
      const text = mergeText(items);
      expect(
        text.includes(