🎨 Palette: Add keyboard shortcuts and score accessibility to Mario game

[EiJackGH]

💡 What

Added visible keyboard shortcuts to the Mario game screen and improved the screen reader accessibility of the score counter.

🎯 Why

Users didn't know which keys to press to jump without reading the source code or guessing. Additionally, visually impaired users wouldn't know when their score was updating.

📸 Before/After

Before: Only "Score: 0" in the top left.
After: "Score: 0" on the left, and "Press [Space] or [↑] to jump" cleanly displayed in the top right.

♿ Accessibility

• Added aria-live="polite" and aria-atomic="true" to the #score element so screen readers will announce the score when it changes.
• Added visual instructions to improve usability for all users without relying on trial and error.

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PR created automatically by Jules for task 17641419728514508121 started by @EiJackGH

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