Storybook: Add BorderRadiusControl story

[Sukhendu2002]

Part of #67165

What?

This PR will add stories for BorderRadiusControl component in the Storybook.

Testing Instructions

1. Run npm run storybook:dev
2. Open the storybook on http://localhost:50240/
3. Check the BorderRadiusControl stories.

Screenshots or screencast

[github-actions]

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Co-authored-by: Sukhendu2002 <[email protected]>
Co-authored-by: t-hamano <[email protected]>

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[Sukhendu2002]

Hi @t-hamano, I’ve updated the PR to include the suggested changes for improving code consistency. Feel free to take a look whenever you have time. Thanks!

[t-hamano]

Thanks for the PR!

I noticed that this component doesn’t have a README.

I believe that every component published to Storybook should have a README so that developers can easily implement the component (See #22891).

If you don’t mind, could you work on creating the README first? Feel free to contact me once the PR is complete 👍

Thank you!