message: Implement `Clone` for `pane_grid::State`
diff: @@ -21,7 +21,7 @@ use std::collections::HashMap;
  /// [`Pane`]: struct.Pane.html
  /// [`Split`]: struct.Split.html
  /// [`State`]: struct.State.html
  -#[derive(Debug)]
  +#[derive(Debug, Clone)]
  pub struct State<T> {
  pub(super) panes: HashMap<Pane, T>,
  pub(super) internal: Internal,
  @@ -248,7 +248,7 @@ impl<T> State<T> {
  }
  }
  -#[derive(Debug)]
  +#[derive(Debug, Clone)]
  pub struct Internal {
  layout: Node,
  last_id: usize,
  