Readonly~feed: ScreenFeedMarker<Optional Readonly~items?: ScreenListItem<Page, ScreenHandle>The handles of the feed's items, a type only: swipeableFeed reads it to
type onSwipe's two arguments as the feed's own item handles. Never set
at run time.
A feed screen: what
defineFeedScreenreturns. A screen definition whose handle is one page of the feed:items, that page's items, andnextPage, the instance of the next page.