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)_.
pending("Worker is not supported in Node.js.");
      }
      const worker = new PDFWorker({ name: "test1" });
      const loadingTask = getDocument(
        buildGetDocumentParams(basicApiFileName, {
          worker,
        })
      );
      loadingTask.promise.then(function () {
        const docWorker = loadingTask._worker;
        expect(!!docWorker).toEqual(false);
        
        const messageHandlerPort = loadingTask._transport.messageHandler.comObj;
        expect(messageHandlerPort === worker.port).toEqual(true);
      });
      const destroyPromise = loadingTask.promise.then(function () {
        return loadingTask.destroy();
      });
      await destroyPromise;
      expect(worker.destroyed).toEqual(false);
      worker.destroy();
    });
    it("creates more than one worker", async function () {
      if (isNodeJS) {
        pending("Worker is not supported in Node.js.");
      }
      const worker1 = new PDFWorker({ name: "test1" });
      const worker2 = new PDFWorker({ name: "test2" });
      const worker3 = new PDFWorker({ name: "test3" });
      await Promise.all([worker1.promise, worker2.promise, worker3.promise]);