Package and upload

[markhicken]

Description

Build and upload the extension package artifact as part of the CI workflow.

Related Issue

Motivation and Context

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• I have updated the Experience League documentation for the Core Extension
• All tests pass and I've made any necessary test changes.
• I have run the extension sandbox successfully.