chore: update sign-in UI and logic

[bcree11]

• Update landing page's sign in UI
• Update sign in/out logic

[github-actions[bot]]

instant-apps-components

The following PR has been closed and merged. - [link to PR]()

• NPM Version: 1.0.0-beta.249 -link
• Repo Version: 1.0.0-beta.250 -link

If you want to publish, your Repo version should be updated and differ from the current version on NPM

To publish instant-apps-components to NPM

If you would like to follow this PR up with a publish, please proceed to the actions tab and manually run the publish.