Expose AnyContainer in prompt_toolkit.layout.

This is often used in type annotations.

Author: jonathanslenders

prompt_toolkit/layout/__init__.py

@@ -45,6 +45,7 @@
 
 """
 from .containers import (
+    AnyContainer,
     ColorColumn,
     ConditionalContainer,
     Container,
@@ -104,6 +105,7 @@
     "to_dimension",
     "is_dimension",
     # Containers.
+    "AnyContainer",
     "Container",
     "HorizontalAlign",
     "VerticalAlign",