⭐️ Impl: UIWindow+WindowMetadata

Related:
* `TODO:2023-03-30-20-13-10` - Impl: `UIWindow.windowID`.

ios/src_library/Helpers+Utilities/UIWindow+WindowMetadata.swift

@@ -0,0 +1,48 @@
+//
+//  UIWindow+WindowMetadata.swift
+//  react-native-ios-modal
+//
+//  Created by Dominic Go on 3/30/23.
+//
+
+import Foundation
+
+
+fileprivate final class WindowMetadata {
+  static var counterID = -1;
+
+  let id: Int = {
+    WindowMetadata.counterID += 1;
+    return WindowMetadata.counterID;
+  }();
+
+  let uuid = UUID();
+};
+
+
+public extension UIWindow {
+
+  fileprivate static let windowMetadataMap = NSMapTable<UIWindow, WindowMetadata>(
+    keyOptions: .weakMemory,
+    valueOptions: .strongMemory
+  );
+
+  fileprivate var windowMetadata: WindowMetadata {
+    if let windowMetadata = Self.windowMetadataMap.object(forKey: self) {
+      return windowMetadata;
+    };
+
+    let windowMetadata = WindowMetadata();
+    Self.windowMetadataMap.setObject(windowMetadata, forKey: self);
+
+    return windowMetadata;
+  };
+
+  var windowID: Int {
+    self.windowMetadata.id;
+  };
+
+  var windowUUID: UUID {
+    self.windowMetadata.uuid;
+  };
+};