Add support for LegendList in MessageList

[arekkubaczkowski]

Motivation While the library already allows swapping out the list component, LegendList handles list inversion differently, which makes it incompatible out of the box for chat UIs. Proper support would require internal adjustments, especially around how inverted lists are handled (e.g. scroll anchoring, loading more messages, maintaining scroll position).

I’ve tested LegendList with a chat view and the performance improvement is significant — smoother scrolling and much lower render times on large message lists.

Suggestion: Provide a wrapper or internal integration that handles LegendList’s inversion model and maps the expected props accordingly. Even basic support would unlock better performance for many apps.