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)_.
*
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import {
  AnnotationMode,
  CMapCompressionType,
  createObjectURL,
  createPromiseCapability,
  createValidAbsoluteUrl,
  InvalidPDFException,
  MissingPDFException,
  OPS,
  PasswordResponses,
  PermissionFlag,
  shadow,
  UnexpectedResponseException,
  UNSUPPORTED_FEATURES,
  Util,
  VerbosityLevel,
} from "./shared/util.js";
import {
  build,
  getDocument,
  LoopbackPort,
  PDFDataRangeTransport,
  PDFWorker,