feat: add thirdweb x402 guide + video from bera summit

[okjintao]

…berachain

Guide Contribution PR

Description

Type of Change

• ✨ New guide/example
• 📝 Update to existing guide/example
• 🐛 Bug fix in a guide/example
• 🎨 Style/formatting update
• ♻️ Refactor (no functional changes)
• Other (please describe):

Guide Details

• Guide Name:
• Category: (e.g., Smart Contracts, Frontend, Infrastructure, Tooling)
• Dependencies Added:
• Network(s) Used: (e.g., Bepolia, Mainnet, Local)
• Entry Point: (e.g., script, README section, etc.)

Checklist

• The guide/example is clear and easy to follow
• All steps are reproducible (instructions/scripts work as described)
• All new/changed code is commented where necessary
• Documentation is updated (README, inline docs, etc.)
• No sensitive information or secrets are included
• Example runs without errors or warnings
• (If applicable) Screenshots or output are included for clarity

Additional Notes

[camembera]

@okjintao needs 'pnpm format'