refactor: improvements and fixes to ButtonLink and SiteNotificationAlert

[sourcefilter]

QA issues and styling, plus a refactor of css transitions to animate the clip-path property

[github-actions[bot]]

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[github-actions[bot]]

🚀 Deployed on https://deploy-preview-277--ucla-library-storybook.netlify.app

[sourcefilter]

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[pghorpade]

:tada: This PR is included in version 2.20.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: