fix: Define typing as a package to support submodules

The usage I described in the description was not actually possible:

>- The top-level object `ThemeConfig` is exported to `altair.typing`> - All others are accessible via `altair.typing.theme`.

This resolves the `ModuleNotFoundError` that would get raised when trying this

altair/typing.py → altair/typing/__init__.py

@@ -51,10 +51,10 @@
     "theme",
 ]
 
-import altair.vegalite.v5.schema._config as theme
+from altair.typing import theme
+from altair.typing.theme import ThemeConfig
 from altair.utils.schemapi import Optional
 from altair.vegalite.v5.api import ChartType, is_chart_type
-from altair.vegalite.v5.schema._config import ThemeConfig
 from altair.vegalite.v5.schema.channels import (
     ChannelAngle,
     ChannelColor,

altair/typing/theme.py

@@ -0,0 +1 @@
+from altair.vegalite.v5.schema._config import *  # noqa: F403

altair/vegalite/v5/schema/_config.py

@@ -10,7 +10,7 @@
     from typing import TypedDict
 else:
     from typing_extensions import TypedDict
-
+from ._typing import PaddingKwds, RowColKwds
 
 if TYPE_CHECKING:
     # ruff: noqa: F405

tools/generate_schema_wrapper.py

@@ -1076,6 +1076,7 @@ def vegalite_main(skip_download: bool = False) -> None:
         HEADER,
         "from typing import Any, TYPE_CHECKING, Literal, Sequence, TypedDict, Union",
         import_typing_extensions((3, 14), "TypedDict", include_sys=True),
+        f"from ._typing import {ROW_COL_KWDS}, {PADDING_KWDS}",
         "\n\n",
         import_type_checking("from ._typing import * # noqa: F403"),
         "\n\n",