feat(NIP-22): advertise support for event created_at limits

The `reject_future_limits` option can now be disabled, and is by
default.

NIP-11 advertises support for created_at limits.

The message for future-dated events has been modified, to be closer to
the recommended example in the NIP.

src/info.rs

@@ -35,7 +35,7 @@ impl From<config::Info> for RelayInfo {
             description: i.description,
             pubkey: i.pubkey,
             contact: i.contact,
-            supported_nips: Some(vec![1, 2, 11, 15, 16]),
+            supported_nips: Some(vec![1, 2, 11, 15, 16, 22]),
             software: Some("https://git.sr.ht/~gheartsfield/nostr-rs-relay".to_owned()),
             version: CARGO_PKG_VERSION.map(|x| x.to_owned()),
         }