docs: update relay example to use current terminology

[achingbrain]

Updates the example to reflect current terminology.

Replace references to "auto relay" to just "relay address"

Adds section about configuring auto-tls as an alternative to manually setting up nginx/SSL

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works