PageSift v1.0.0 third-party notices

This extension includes the following open-source software:

- Mozilla Readability, licensed under the Apache License 2.0
  https://github.com/mozilla/readability
  https://www.apache.org/licenses/LICENSE-2.0

- Turndown, licensed under the MIT License
  https://github.com/mixmark-io/turndown

- Turndown Plugin GFM, licensed under the MIT License
  https://github.com/mixmark-io/turndown-plugin-gfm

- JSZip, licensed under the MIT License
  https://github.com/Stuk/jszip

- TOON reference encoder, licensed under the MIT License
  https://github.com/toon-format/toon

- pdf-lib, licensed under the MIT License
  https://github.com/Hopding/pdf-lib

The full project notices are included with the PageSift release materials.
