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)_.
setPDFNetworkStreamFactory,
  version,
} from "./display/api.js";
import {
  getFilenameFromUrl,
  getPdfFilenameFromUrl,
  getXfaPageViewport,
  isPdfFile,
  isValidFetchUrl,
  loadScript,
  PDFDateString,
  PixelsPerInch,
  RenderingCancelledException,
} from "./display/display_utils.js";
import { AnnotationLayer } from "./display/annotation_layer.js";
import { GlobalWorkerOptions } from "./display/worker_options.js";
import { isNodeJS } from "./shared/is_node.js";
import { renderTextLayer } from "./display/text_layer.js";
import { SVGGraphics } from "./display/svg.js";
import { XfaLayer } from "./display/xfa_layer.js";
const pdfjsVersion =
  typeof PDFJSDev !== "undefined" ? PDFJSDev.eval("BUNDLE_VERSION") : void 0;
const pdfjsBuild =
  typeof PDFJSDev !== "undefined" ? PDFJSDev.eval("BUNDLE_BUILD") : void 0;
if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
  const streamsPromise = Promise.all([
    import("pdfjs/display/network.js"),
    import("pdfjs/display/fetch_stream.js"),
  ]);
  setPDFNetworkStreamFactory(async params => {