chore(content-sharing): Create a story for SharingModal component

[devin-ai-integration]

Description

Added a Storybook story for the SharingModal component to improve component documentation and testing capabilities. The story includes:

• Default configuration with mock API responses
• Proper TypeScript types and documentation
• Integration with existing mock data from USMMocks

Related issues

N/A

Manual testing steps

3. Go to the latest build of storybook in this PR
4. Navigate to the SharingModal component in the Components/Elements/ContentSharing folder.

Screenshots/Recordings

Screenshots will be added once the Storybook environment is properly configured.

Pre-merge author checklist

• I have followed Box Contributing Standards.
• I have followed Box Developing Standards.
• I have completed the PR template to the best of my ability
• I have included tests if applicable
• I have documented my code using JSDoc format if applicable
• I have applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I have 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.

[devin-ai-integration]

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