docs: update discord invite

[aaa123eee]

What is it?

• [ ] Feature / enhancement
• [ ] Bug
• [x] Docs / tests

Description

Thanks to @gioboa for providing a valid link https://github.com/BuilderIO/partytown/pull/606#issuecomment-2315322215

closes #547

Checklist:

• [ ] My code follows the developer guidelines of this project
• [ ] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [ ] Added new tests to cover the fix / functionality