storage: expand docs for trait with an example of where it's used.

src/storage.rs

@@ -13,7 +13,15 @@ pub(crate) trait SealedStorage {
 /// - [`OwnedStorage`]: stores the data in an array `[T; N]` whose size is known at compile time.
 /// - [`ViewStorage`]: stores the data in an unsized `[T]`.
 ///
-/// This allows containers to be generic over either sized or unsized storage.
+/// This allows containers to be generic over either sized or unsized storage. For example,
+/// the [`vec`](crate::vec) module contains a [`VecInner`](crate::vec::VecInner) struct
+/// that's generic on [`Storage`], and two type aliases for convenience:
+///
+/// - [`Vec<T, N>`](crate::vec::Vec) = `VecInner<T, OwnedStorage<N>>`
+/// - [`VecView<T>`](crate::vec::VecView) = `VecInner<T, ViewStorage>`
+///
+/// `Vec` can be unsized into `VecView`, either by unsizing coercions such as `&mut Vec -> &mut VecView` or
+/// `Box<Vec> -> Box<VecView>`, or explicitly with [`.as_view()`](crate::vec::Vec::as_view) or [`.as_mut_view()`](crate::vec::Vec::as_mut_view).
 ///
 /// This trait is sealed, so you cannot implement it for your own types. You can only use
 /// the implementations provided by this crate.