feat: support contents display mode

Author: OhKanghoon

Sources/Swift/FlexLayout.swift

@@ -1466,6 +1466,10 @@ public final class Flex {
         case flex
         /// With this value, the item will be hidden and not be calculated
         case none
+        /// With this value, the node is removed from the layout flow, while its children are preserved and hoisted.
+        /// This allows higher-level UI frameworks to compose wrapper components (e.g., to handle events)
+        /// without influencing the layout of child nodes.
+        case contents
     }
 
     /*public enum Overflow {

Sources/Swift/Impl/FlexLayout+Enum.swift

@@ -114,6 +114,7 @@ extension Flex.Display {
         switch self {
         case .flex: return YGDisplay.flex
         case .none: return YGDisplay.none
+        case .contents: return YGDisplay.contents
         }
     }
 }