chore: inject website bundle script into the head to prevent flash of unstyled content

[chrisdholt]

Description

This PR shifts the bundle for the website homepage from the end of the body to the head. Doing so will block the rendering of the page for the bundle which will prevent a flash of unstyled content and ensure that the web components and styles making up the page load together.

Motivation & context

Issue type checklist

• Chore: A change that does not impact distributed packages.
• Bug fix: A change that fixes an issue, link to the issue above.
• New feature: A change that adds functionality.

Is this a breaking change?

• This change causes current functionality to break.

Adding or modifying component(s) in @microsoft/fast-components checklist

• I have added a new component
• I have modified an existing component
• I have updated the definition file
• I have updated the configuration file

Process & policy checklist

• 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.