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)_.
it("gets non-default viewer preferences", async function () {
      const prefs = await pdfDocument.getViewerPreferences();
      expect(prefs).toEqual({ Direction: "L2R" });
    });
    it("gets default open action", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("tracemonkey.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const openAction = await pdfDoc.getOpenAction();
      expect(openAction).toEqual(null);
      await loadingTask.destroy();
    });
    it("gets non-default open action (with destination)", async function () {
      const openAction = await pdfDocument.getOpenAction();
      expect(openAction.dest).toEqual([
        { num: 15, gen: 0 
        { name: "FitH" 
        null,
      ]);
      expect(openAction.action).toBeUndefined();
    });
    it("gets non-default open action (with Print action)", async function () {
      
      const loadingTask1 = getDocument(
        buildGetDocumentParams("bug1001080.pdf")
      );
      
      
      const loant(