back-to-top(refactor): update element compliant with Auro dev specs

[littleninja]

Alaska Airlines Pull Request

Summary:

This change aims to address any gaps required to meet Auro development standards. Design artwork and UI Kit are still missing. Also includes minor tweaks to documentation.

Type of change:

Please delete options that are not relevant.

• [X] Revision of an existing capability

Checklist:

• [X] My update follows the CONTRIBUTING guidelines of this project
• [X] I have performed a self-review of my own update

By submitting this Pull Request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Pull Requests will be evaluated by their quality of update and whether it is consistent with the goals and values of this project. Any submission is to be considered a conversation between the submitter and the maintainers of this project and may require changes to your submission.

Thank you for your submission!
-- Auro Design System Team

[littleninja]

@blackfalcon when you have time, this pull request aims to make back-to-top Auro compliant. Please feel encouraged to go beyond the changes committed and identify any remaining gaps in the source code that need fixed.

If your exploration surfaces a list, I can switch this to a draft pull request. Thank you.