Function mailboxesFromEvent

mailboxesFromEvent(event: NostrEvent | undefined): Mailboxes
Read a NIP-65 list. An unmarked r tag is both an inbox and an outbox; a tag with any other marker, or a value that is not a ws: or wss: URL, is skipped. applesauce's getInboxes is not used because its URL check refuses top-level domains longer than six letters.
Parameters
- event: NostrEvent | undefined
  A kind 10002 event, or nothing.
Returns Mailboxes
Normalised inboxes and outboxes; empty for no event.
Example
```
mailboxesFromEvent({ ...event, tags: [['r', 'wss://a.example'], ['r', 'wss://b.example', 'read']] });
// { inboxes: ['wss://a.example/', 'wss://b.example/'], outboxes: ['wss://a.example/'] }
```