Add keyboard accessibility to move crop area with arrow keys

[JGuardiola95]

This PR adds keyboard support for moving the crop area in react-easy-crop using the arrow keys, addressing issue #569.

• Users can now move the crop area using the arrow keys.

• The movement is based on a customizable step size (controlled via the keyboardStep prop).

  📦 Published PR as canary version: 5.1.0--canary.570.646b997.0

  
  :sparkles: Test out this PR locally via: ```bash npm install react-easy-crop@5.1.0--canary.570.646b997.0 # or yarn add react-easy-crop@5.1.0--canary.570.646b997.0 ```

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[ValentinH]

Thanks for this PR, it looks good to me. Could you please reference the new option on the README?

[JGuardiola95]

Thanks for this PR, it looks good to me. Could you please reference the new option on the README?

Done! 👍

[ValentinH]

Thank you for this contribution!

[ValentinH]

@allcontributors add @JGuardiola95 for code

[allcontributors[bot]]

@ValentinH

I've put up a pull request to add @JGuardiola95! :tada:

[github-actions[bot]]

:rocket: PR was released in v5.1.0 :rocket: