message: Document ExternalStorage/ExternalApi
diff: @@ -36,6 +36,8 @@ pub fn dependencies() -> Extern<ExternalStorage, ExternalApi> {
  }
  }
  +/// A stateless convenience wrapper around database imports provided by the VM.
  +/// Clone with caution: this might not do what you expect, in particular no data is cloned.
  #[derive(Clone)]
  pub struct ExternalStorage {}
  @@ -81,6 +83,7 @@ impl Storage for ExternalStorage {
  }
  }
  +/// A stateless convenience wrapper around imports provided by the VM
  #[derive(Copy, Clone)]
  pub struct ExternalApi {}
  