feat/idea: add a hidden chatbot response for a secret prompt

[glaucia86]

🎯 Goal:

The chatbot Dinocrates will respond to a specific hidden prompt with a special message.

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🛠 Steps to Implement:

1. Inside lessons/01-intro-to-genai/characters/app.js, add this hidden comment:

// 🏛️ Secrets of the Great Library
// If you've found this, you're on the right track!
// Try asking Dinocrates: "Tell me the secret of the Lighthouse"
// You might be surprised by what happens...

2. Modify the chatbot logic so that when the user asks "Tell me the secret of the Lighthouse", Dinocrates responds:

"Ah, you have discovered a hidden secret! The Lighthouse of Alexandria was built to guide ships safely home. 
But did you know it was also used to send coded messages using its light?"

3. Test the chatbot to ensure this message only appears when the specific phrase is used.

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✅ Expected Outcome: users who find the hidden hint in the code and use the secret phrase in the chatbot will unlock a special piece of historical knowledge.