fix: legacy - use Buffer.from() instead of btoa()

[Luna-devv]

Description

Fix homepage example for "Work with Threads": btoa("") is a legacy function, Buffer.from("").toString("base64") should be used instead.

Validation

Related Issues

Check List

• [x] I have read the Contributing Guidelines and made commit messages that follow the guideline.
• [x] I have run npx turbo format to ensure the code follows the style guide.
• [x] I have run npx turbo test to check if all tests are passing.
• [x] I have run npx turbo build to check if the website builds without errors.
• [x] I've covered new added functionality with unit tests if necessary.