new prop for List.Accordion to optionally expand upwards instead of downwards

**Is your feature request related to a problem? Please describe.**
List.Accordion always expands downwards. It would be great to have a second option which is 'upwards'

**Describe the solution you'd like**
Introduce a new prop such as expandDirection = 'downwards' (default) | 'upwards'

**Describe alternatives you've considered**
none

**Additional context**
none

Start by locating the List.Accordion implementation and its existing component tests, then trace how expansion currently determines layout direction. Done means the component accepts the requested direction option, preserves downward expansion by default, supports upward expansion, and has coverage for both behaviors.

Written by the indexing model from the issue text.