Bug - Dropdown - popperProps doesn't support appendTo

[wise-king-sullyman]

Describe the problem
Currently we can't customize what the menu appends to in Dropdown without type casting as DropdownPopperProps doesn't support the appendTo property.

How do you reproduce the problem?
Attempt to pass the appendTo property to popperProps and view that it throws a type error requiring type casting.

Expected behavior
A clear and concise description of the expected behavior.
We should be able to pass the appendTo property to popperProps.

This issue will help to properly resolve patternfly/patternfly#5865 in a non-breaking way.