Add annotations to docutils.parsers.rst.directives.parts (#11667)

stubs/docutils/docutils/parsers/rst/directives/parts.pyi

@@ -1,3 +1,10 @@
-from _typeshed import Incomplete
+from collections.abc import Sequence
 
-def __getattr__(name: str) -> Incomplete: ...
+from docutils.parsers.rst import Directive
+
+class Contents(Directive):
+    backlinks_values: Sequence[str]
+
+class Sectnum(Directive): ...
+class Header(Directive): ...
+class Footer(Directive): ...