🎨 Palette: Add accessible instructions and score to Mario game

[EiJackGH]

💡 What: Added visible keyboard instructions ("Press Space or Up Arrow to jump") to the Mario game UI. Also added aria-live="polite" and aria-atomic="true" attributes to the score display container.

🎯 Why: Users previously had no immediate visual indication of what keys were required to play the game, leading to initial confusion. Adding these clear, unobtrusive instructions improves discoverability and the overall onboarding experience.

📸 Before/After: The instructions are now displayed subtly below the score in the top left corner, matching the existing visual hierarchy of the UI.

♿ Accessibility: The newly added aria-live and aria-atomic attributes ensure that screen readers can correctly and cleanly announce dynamic score updates to visually impaired users during gameplay, while the static instructions are kept in a separate sibling container to avoid redundant voice-overs.

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PR created automatically by Jules for task 2420633220270642582 started by @EiJackGH

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