Fix/shortcuts and overlap

[yashraj4]

🎯 What issue does this address?

Currently, players are not aware of the available keyboard shortcuts in the game. There's no way to discover controls like Space or R without guessing or reading the source code. This PR solves that by adding an in-game help panel that lists all the controls.

✨ What does this change?

This pull request implements a new keyboard shortcuts help overlay and adds new hotkeys for a better user experience:

• Keyboard Shortcuts Overlay: A new modal (#shortcuts-help) is added to index.html. It's styled in css/style.css to match the "Game Over" results panel for a consistent UI.
• Toggle with H key: Pressing H now toggles this new help panel on and off (Js/script.js).
• Toggle Mute with M key: A new key listener for M is added to Js/script.js, which calls the toggleMute() function, allowing players to mute/unmute audio with their keyboard.
• Escape Key Functionality: The Escape key can now be used to close the shortcuts panel (or the "Game Over" panel, if that is open).

Checklist:

• New functionality meets the goals defined in the linked issue.
• If changing the UI or game experience, screenshots or a GIF are included below.
• Code is formatted cleanly (ran Prettier/ESLint locally).
• All CI/CD checks in this PR passed.

🖼️ Screenshots / Video Preview

Before Changes	After Changes
No help overlay available. Players cannot see keyboard shortcuts.	A new help overlay is available, toggled with the 'H' key.

🔗 Related Issue(s)

Fixes #72

✅ Checklist (Required)

• I have read the project's [CONTRIBUTING.md] guidelines.
• My code follows the project's coding style and conventions.
• I have performed a self-review of my own code.
• My changes generate no new errors or warnings in the browser console.
• I have tested my changes locally on the Vercel-simulated environment (if applicable).
• For UI changes, I have tested on different screen sizes (responsive design check).
• My commit message(s) are clear and descriptive.

[vercel]

@yashraj4 is attempting to deploy a commit to the Maitri Vaghasiya's projects Team on Vercel.

A member of the Team first needs to authorize it.

[yashraj4]

@maitri-vv , can you pls authorize the deploy, so that I can see if the preview is working or not this time?