Add MyNextBrowser to the list of tools

[soumikmahato]

📝 New Tool Information

• Tool Name: MyNextBrowser
• Description: (max 1 sentence) Turn Any Browser into Agentic AI
• Tool URL: https://www.mynextbrowser.com
• Altern.ai page link: (if available)

📌 Description

Added new tool to under ChatGPT extensions section.

✅ Checklist

• I have read the Contribution Guidelines
• Only one tool is modified in this PR
• All required fields (name, description, URL, altern.ai link if available) are provided
• The tool link is valid and accessible
• The tool is not already listed
• The tool is placed in the correct category
• The tool is added at the end of its category
• No unrelated changes included in this PR

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🛠 Type of Change

• 📚 Documentation / README update
• ➕ Adding a new AI tool
• 🗑 Removing a deprecated/invalid AI tool
• ♻️ Refactoring or reorganizing existing entries
• 🐛 Bug fix
• Other (please specify):

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📷 Screenshots / Demo (if applicable)

MyNextBrowser Website

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💡 Additional Notes