[Feature] Initial NIP-26 support (#25)

* adds initial NIP-26 support

* Update README.md

* Update README.md

nostr/delegation.py

@@ -0,0 +1,32 @@
+import time
+from dataclasses import dataclass
+
+
+@dataclass
+class Delegation:
+    delegator_pubkey: str
+    delegatee_pubkey: str
+    event_kind: int
+    duration_secs: int = 30*24*60  # default to 30 days
+    signature: str = None  # set in PrivateKey.sign_delegation
+
+    @property
+    def expires(self) -> int:
+        return int(time.time()) + self.duration_secs
+    
+    @property
+    def conditions(self) -> str:
+        return f"kind={self.event_kind}&created_at<{self.expires}"
+    
+    @property
+    def delegation_token(self) -> str:
+        return f"nostr:delegation:{self.delegatee_pubkey}:{self.conditions}"
+
+    def get_tag(self) -> list[str]:
+        """ Called by Event """
+        return [
+            "delegation",
+            self.delegator_pubkey,
+            self.conditions,
+            self.signature,
+        ]