chore: update typescript skills and fast element design files

[janechu]

Pull Request

📖 Description

Update the typescript skill for agents and the design file for @microsoft/fast-element which had a reference to the outdated compose method.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.