Move third-party content included in Cesium itself to the correct section of the document

[shunter]

Specifically, GraphemeSplitter and bitmap-sdf were incorrectly added to the Example Applications section.

(errors made in #7280 and #7730 respectively)

Also fixed some other typographical errors.

[cesium-concierge]

Thanks for the pull request @shunter!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[hpinkos]

Thanks @shunter!