improve type annotations in 'docutils.readers' (#11490)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

stubs/docutils/docutils/readers/__init__.pyi

@@ -1,3 +1,26 @@
-from _typeshed import Incomplete
+from typing import Any, ClassVar
 
-def __getattr__(name: str) -> Incomplete: ...
+from docutils import Component, nodes
+from docutils.frontend import Values
+from docutils.io import Input
+from docutils.parsers import Parser
+from docutils.transforms import Transform
+
+class Reader(Component):
+    component_type: ClassVar[str]
+    config_section: ClassVar[str]
+    def get_transforms(self) -> list[type[Transform]]: ...
+    def __init__(self, parser: Parser | None = None, parser_name: str | None = None) -> None: ...
+    parser: Parser | None
+    source: Input | None
+    input: str | Any | None
+    def set_parser(self, parser_name: str) -> None: ...
+    def read(self, source: Input, parser: Parser, settings: Values) -> nodes.document: ...
+    document: nodes.document
+    def parse(self) -> None: ...
+    def new_document(self) -> nodes.document: ...
+
+class ReReader(Reader):
+    def get_transforms(self) -> list[type[Transform]]: ...
+
+def get_reader_class(reader_name: str) -> type[Reader]: ...