Adds Item protocol

Author: Maxcode123

src/syntactes/_item.py

@@ -1,9 +1,14 @@
-from typing import Optional
+from typing import Optional, Protocol
 
 from syntactes.rule import Rule
 from syntactes.token import Token
 
 
+class Item(Protocol):
+    rule: Rule
+    position: int
+
+
 class LR0Item:
     """
     Item of LR0 parser. Contains rule and current position in rule.