Add Valera relays to bootstrap list

[Zk2u]

Following up on #471, here is Valera's relay network. These are anycasted on our server infrastructure, and run nostr-rs-relay.

[jb55]

nostr-rs-relay can't really handle the load for our users unfortunately

[Zk2u]

the endpoint is load balanced across multiple datacenters - it's not a single relay :)

is there a reason nostr-rs-relay won't work for this many users? it's tokio-based and currently the fastest i've used. do you recommend any other implementations?