Feature: Allow editing relays

[Giszmo]

In the settings, add a list of relays.
As a first step, copy how Astral does it.

Mark the first relay as "primary" relay. Here we will get events from first. The others might get updates more throttled to avoid burst flooding with duplicate events.

With this issue, all relays are being connected at startup as equals.

[snuffyDev]

I’ll work on this if needed!