message: Add Display for FrozenRef
diff: use std::{
  borrow::Borrow,
  cmp::Ordering,
  + fmt::{self, Display, Formatter},
  hash::{Hash, Hasher},
  ops::Deref,
  ptr,
  @@ -56,6 +57,12 @@ impl<'f, T: 'f + ?Sized> FrozenRef<'f, T> {
  }
  }
  +impl<'f, T: ?Sized + Display> Display for FrozenRef<'f, T> {
  + fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
  + self.value.fmt(f)
  + }
  +}
  +
  impl<'f, T: ?Sized> Deref for FrozenRef<'f, T> {
  type Target = T;
  