message: Reintroduce the key binding for split panes
  It was lost in a merge.
diff: @@ -47,6 +47,8 @@ static constexpr std::string_view SwitchToTab6Key{ "switchToTab6" };
  static constexpr std::string_view SwitchToTab7Key{ "switchToTab7" };
  static constexpr std::string_view SwitchToTab8Key{ "switchToTab8" };
  static constexpr std::string_view OpenSettingsKey{ "openSettings" };
  +static constexpr std::string_view SplitHorizontalKey{ "splitHorizontal" };
  +static constexpr std::string_view SplitVerticalKey{ "splitVertical" };
  // Specifically use a map here over an unordered_map. We want to be able to
  // iterate over these entries in-order when we're serializing the keybindings.
  @@ -89,6 +91,8 @@ static const std::map<std::string_view, ShortcutAction, std::less<>> commandName
  { SwitchToTab6Key, ShortcutAction::SwitchToTab6 },
  { SwitchToTab7Key, ShortcutAction::SwitchToTab7 },
  { SwitchToTab8Key, ShortcutAction::SwitchToTab8 },
  + { SplitHorizontalKey, ShortcutAction::SplitHorizontal },
  + { SplitVerticalKey, ShortcutAction::SplitVertical },
  };
  // Function Description:
  