WIP: Add inheritance_diagram_direction option

Author: johnslavik

src/mkdocstrings_handlers/python/_internal/config.py

@@ -488,6 +488,14 @@ class PythonInputOptions:
         ),
     ] = 2
 
+    inheritance_diagram_direction: Annotated[
+        Literal["TB", "TD", "BT", "RL", "LR"],
+        _Field(
+            group="docstrings",
+            description="Set the direction of the Mermaid chart presenting the inheritance diagram of a class.",
+        ),
+    ]
+
     inherited_members: Annotated[
         bool | list[str],
         _Field(