fix: update supported nips in readme (#164)

* fix: update supported nips in readme

* fix: add new line after nip list

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Co-authored-by: Ricardo Arturo Cabral Mejía <[email protected]>

Author: antonleviathan

README.md

@@ -59,6 +59,7 @@ NIPs with a relay-specific implementation are listed here.
 - [x] NIP-26: Delegated Event Signing
 - [x] NIP-28: Public Chat
 - [x] NIP-33: Parameterized Replaceable Events
+- [x] NIP-40: Expiration Timestamp
 - [x] NIP-111: Relay Information Document Extensions
 
 ## Requirements