Storybook: Add stories for BlockTitle Component

[SainathPoojary]

Part of #67165

What?

This PR adds Storybook stories for the BlockTitle component to improve component documentation and testability.

Why?

• Provide visual documentation for the BlockTitle component
• Enable interactive testing of different block title scenarios
• Improve development experience for Block Editor components

Testing Instructions

1. Run npm run storybook:dev
2. Open Storybook at http://localhost:50240/
3. Verify the following stories are present and functioning:
   • Default block title rendering
   • Block title with maximum length truncation
   • Different block type titles (paragraph, heading, nested blocks)

Screencast

Screen.Recording.2024-11-22.at.6.53.22.PM.mov

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Co-authored-by: SainathPoojary <[email protected]>

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