Add a RenderableFASTElement and default shadow options

[janechu]

Pull Request

📖 Description

This change:

• Requires that using @microsoft/fast-html rendered markup include hydratable markup.
• Adds default shadowOptions so they do not need to be passed
• Adds a RenderableFASTElement export which will automatically add and remove the defer-hydration attributes

✅ 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.