feat(APP-3652): Add variant property to ToggleGroup component, support XS size on Avatar component

[cgero-eth]

Description

• Add variant property to ToggleGroup component to support "space-between" spacing
• Add XS size to Avatar core component

Task: APP-3652

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• Manually smoke tested the functionality locally
• Confirmed there are no new warnings or errors in the browser console
• Made the corresponding changes to the documentation
• Added tests that prove my fix is effective or that my feature works
• Updated the CHANGELOG.md file after the [UPCOMING] title and before the latest version
• (For User Stories only) Double-checked that all Acceptance Criteria are satisified
• Confirmed there are no new warnings on automated tests
• Selected the correct base branch
• Commented the code in hard-to-understand areas
• Followed the code style guidelines of this project
• Reviewed that the files changed in GitHub’s UI reflect my intended changes
• Confirmed the pipeline checks are not failing

[shan8851]

LGTM!