Add AI-Ready updates to voice-ivr project

[micaswyers-work]

Description

This commit updates the voice-ivr function template with some "AI-Ready additions, specifically AGENTS.md and .env.example. Additionally, it updates the README.

Checklist

• I ran npm test locally and it passed without errors.
• I acknowledge that all my contributions will be made under the project's license.

Related issues

[twiliojosh]

Looks great - just two small comments

[twiliojosh]

🚢

[welcome]

Congratulations on your first contribution to the Twilio Function Templates!
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