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)_.
125,
        0,
      ]);
      await loadingTask.destroy();
    });
    it("gets non-string destination", async function () {
      let numberPromise = pdfDocument.getDestination(4.3);
      let booleanPromise = pdfDocument.getDestination(true);
      let arrayPromise = pdfDocument.getDestination([
        { num: 17, gen: 0 
        { name: "XYZ" 
        0,
        841.89,
        null,
      ]);
      numberPromise = numberPromise.then(
        function () {
          throw new Error("shall fail for non-string destination.");
        
        function (reason) {
          expect(reason instanceof Error).toEqual(true);
        }
      );
      booleanPromise = booleanPromise.then(
        function () {
          throw new Error("shall fail for non-string destination.");
        
        function (reason) {
          expect(reason instanceof Error).toEqual(true);
        }