feat: adding data theme light attribute to stylesheet to provide dyna…

[georgewrmarshall]

Description

This PR addresses the need for flexible theme switching, as discussed in Issue #626. The motivation behind this change is to enhance user experience by allowing dynamic theme changes (light and dark modes) at any level of the application.

The solution involves updating our CSS to explicitly define light and dark mode variables and applying them using the data-theme attribute. This approach ensures that theme changes are seamlessly reflected across the application, regardless of the global theme setting.

Related issues

Fixes: #626

Manual testing steps

1. Run storybook in the extension using yarn storybook
2. Inspect the stylesheet of the design tokens and add ,[data-theme='light'] to root
3. Test the theme switch at a component level by manually adding data-theme="light" or data-theme="dark" to component containers.

Screenshots/Recordings

After

Screencast below shows theming not work but once the data attribute [data-theme='light'] dynamic theming works

after1080.mov

Pre-merge author checklist

• I’ve followed MetaMask Coding Standards.
• I've clearly explained what problem this PR is solving and how it is solved.
• I've linked related issues
• I've included manual testing steps
• I've included screenshots/recordings if applicable
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.
• I’ve properly set the pull request status:
  • In case it's not yet "ready for review", I've set it to "draft".
  • In case it's "ready for review", I've changed it from "draft" to "non-draft".

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.