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)_.
createValidAbsoluteUrl,
  getDocument,
  getFilenameFromUrl,
  getPdfFilenameFromUrl,
  getXfaPageViewport,
  GlobalWorkerOptions,
  InvalidPDFException,
  isPdfFile,
  loadScript,
  LoopbackPort,
  MissingPDFException,
  OPS,
  PasswordResponses,
  PDFDataRangeTransport,
  PDFDateString,
  PDFWorker,
  PermissionFlag,
  PixelsPerInch,
  RenderingCancelledException,
  renderTextLayer,
  shadow,
  SVGGraphics,
  UnexpectedResponseException,
  UNSUPPORTED_FEATURES,
  Util,
  VerbosityLevel,
  version,
  XfaLayer,
};