Relay serviceEndpoint URLs should include trailing slash

[melvincarvalho]

Issue

According to the DID Nostr specification:

Relay URLs at the origin level MUST include a trailing slash (e.g., wss://relay.example.com/).

Currently, the resolver outputs relay URLs without trailing slashes:

{
  "id": "did:nostr:...#1",
  "type": "Relay",
  "serviceEndpoint": "wss://relay.damus.io"
}

Expected

{
  "id": "did:nostr:...#1",
  "type": "Relay", 
  "serviceEndpoint": "wss://relay.damus.io/"
}

Suggested Fix

When constructing the service array, append a trailing slash to relay URLs if not already present:

const relayUrl = url.endsWith('/') ? url : url + '/';

This ensures compliance with the DID Nostr specification's MUST requirement for relay service endpoints.