Function movableContentOf 

pub fn movableContentOf<K: Hash>(
    key: K,
    content: impl Fn() + 'static,
) -> MovableContent

Movable content whose identity is key, the same at every call site.

The keyed twin of rememberMovableContentOf, and the same identity movable uses: content shown by this value and content shown by movable under the same key is one piece of content. Reach for this when the parents that can show it are in different composables, so no single value can be handed to all of them.