Add: Galactic Jet Defender quest

[Akshatshukla-25]

What does this PR do?

Closes #779

Adds Galactic Jet Defender (quests/galactic-jet-defender.html) under the JavaScript Fundamentals category. The quest is a fast-paced 2D retro-arcade space fighter plane shooter game built with HTML5 Canvas and native Web Audio API. Players pilot an Interceptor Falcon fighter jet using WASD / Arrow Keys while continuous dual lasers auto-fire forward against waves of enemy Crimson Vipers and Void Dreadnought battlecruisers.

Type of Change

• New tool / quest
• Enhancement to existing tool
• Bug fix
• Documentation update
• Build system / infrastructure

Screenshot

Checklist

• I have read the Contributing Guide
• My branch follows the naming convention (add/tool-name, feat/description, or fix/description)
• I have tested my changes locally in at least one modern browser

For new tools / quests:

• The quest is a single self-contained .html file in the quests/ folder
• The filename is kebab-case (galactic-jet-defender.html)
• I added an entry to data/quests.json with all required fields
• I added a screenshot as quests/galactic-jet-defender.png next to the HTML file
• No JS frameworks or heavy UI libraries
• I ran node scripts/sort-norm.js data/quests.json to sort and normalize the quests registry
• I ran node scripts/build.js and verified the landing page renders correctly