Added readme for keyboard shortcut

[vk17-starlord]

PR Description

What?
Closes Issue #52063

This PR adds a README.md file for the keyboard-shortcuts component in the Gutenberg project.

Why?
The keyboard-shortcuts component was missing a README.md file, which is crucial for providing documentation and clarity on the component's purpose and usage.

How?

• Created a new README.md file for the keyboard-shortcuts component.
• Detailed the KeyboardShortcuts component, including its usage, available shortcuts, and implementation.
• Followed the structure and content style of the alignment-control README as a reference.

Testing Instructions

1. Navigate to the keyboard-shortcuts component directory.
2. Ensure the new README.md file is present and contains relevant information about the component.
3. Review the content to verify it aligns with Gutenberg documentation standards.

Testing Instructions for Keyboard

• Navigate through the documentation using keyboard shortcuts to ensure accessibility.

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Co-authored-by: vk17-starlord <[email protected]>
Co-authored-by: mburridge <[email protected]>

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