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 { items } = await pdfPage.getTextContent();
      const text = mergeText(items);
      expect(
        text.includes(`Open Sans is a humanist sans serif typeface designed by Steve Matteson.
Open Sans was designed with an upright stress, open forms and a neu-
tral, yet friendly appearance. It was optimized for print, web, and mobile
interfaces, and has excellent legibility characteristics in its letterforms (see
figure \x81 on the following page). This font is available from the Google Font
Directory [\x81] as TrueType files licensed under the Apache License version \x82.\x80.
This package provides support for this font in LATEX. It includes Type \x81
versions of the fonts, converted for this package using FontForge from its
sources, for full support with Dvips.`)
      ).toEqual(true);
      await loadingTask.destroy();
    });
    it("gets text content, with negative spaces (bug 931481)", async function () {
      if (isNodeJS) {
        pending("Linked test-cases are not supported in Node.js.");
      }
      const loadingTask = getDocument(buildGetDocumentParams("bug931481.pdf"));
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const { items } = await pdfPage.getTextContent();
      const text = mergeText(items);
      expect(
        text.includes(`Kathrin Nachbaur
Die promovierte Juristin ist 1979 in Graz geboren und aufgewachsen. Nach
erfolgreichem Studienabschluss mit Fokus auf Europarecht absolvierte sie ein
Praktikum bei Magna International in Kanada in der Human Resources Abteilung.
Anschliessend wurde sie geschult in Human Resources, Arbeitsrecht und