Set __slots__ for PathPlus

Author: domdfcoding

domdf_python_tools/paths.py

@@ -316,6 +316,8 @@ class PathPlus(pathlib.Path):
 		Defaults to Unix line endings (``LF``) on all platforms.
 	"""
 
+	__slots__ = ('_accessor', )
+
 	def __new__(cls, *args, **kwargs):  # noqa D102
 		if cls is PathPlus:
 			cls = WindowsPathPlus if os.name == "nt" else PosixPathPlus