`Path.cwd()` is missing a return type annotation

[purplezimmermann]

Mypy reports:

error: Call to untyped function "cwd" of "Path" in typed context  [no-untyped-call]

–& indeed:

path/path/__init__.py

Lines 254 to 259 in 0f86209

	def cwd(cls):
	"""Return the current working directory as a path object.
	.. seealso:: :func:`os.getcwd`
	"""
	return cls(os.getcwd())