docs: Add docstrings for Identifier, Properties, RecursiveDict

This allows mkdocstrings to generate hyperlinks
to these types in the documentation.

Fixes: #1529

pyiceberg/typedef.py

@@ -74,8 +74,14 @@ def __missing__(self, key: K) -> V:
 
 
 Identifier = Tuple[str, ...]
+"""Type for identifiers in PyIceberg."""
+
 Properties = Dict[str, Any]
+"""A dictionary type for properties in PyIceberg."""
+
+
 RecursiveDict = Dict[str, Union[str, "RecursiveDict"]]
+"""A recursive dictionary type for nested structures in PyIceberg."""
 
 # Represents the literal value
 L = TypeVar("L", str, bool, int, float, bytes, UUID, Decimal, covariant=True)