Improve keyboard accessibility for memory cards and controls

[AditiBS]

📌 Description

This pull request improves the accessibility of the Memory Block Game by adding full keyboard support.
Previously, the game could only be played using mouse or touch input, which limited accessibility for keyboard-only and assistive technology users.

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🔗 Related Issue

Closes: #71

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🛠 Changes Made

• Made all game cards focusable using the Tab key
• Enabled cards to flip using Enter or Space

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✅ Checklist

• I have tested my changes
• My code follows project guidelines
• I have linked the related issue

[FOSSCLUB-LBSITW]

Hi 👋
Thanks for improving keyboard accessibility — this is a great enhancement for usability.
There are currently merge conflicts in script.js and styles.css that need to be resolved before we can proceed.
Could you please update your branch with the latest main and resolve the conflicts?
Let us know if you need any help. Thanks!