docs: add ServerBuddy to popular server lists

[bullishlucas]

Summary

• Adds ServerBuddy to the guide's Popular Minecraft Server Lists section.
• Notes its live status, player-count history, uptime data, and lack of voting so readers can distinguish it from the vote-driven lists already documented.

Disclosure

I help run ServerBuddy and am proposing an affiliated link. There is no paid or affiliate placement involved.

Verification

• Ran git diff --check with no errors.
• Confirmed https://serverbuddy.net/ returns HTTP 200 on 2026-08-21.