⭐️ Impl: RNIModalIdentity.modalIndexPrev

Related:
* `TODO:2023-03-04-13-15-11` - Refactor: Update Modal Events.
*  `TODO:2023-03-30-16-25-01` - Impl: `RNIModal.modalIndexPrev`.

Summary:
* Update `RNIModalIdentity` - Add `modalIndexPrev` property.
* Update `RNIModalView` - Add `modalIndexPrev` property.
* Update `RNIModalManager` - Impl. logic to init. + update `RNIModalIdentity.modalIndexPrev`.

ios/src_library/React Native/RNIModal/RNIModal.swift

@@ -33,7 +33,10 @@ public protocol RNIModalIdentity: AnyObject {
 
   var modalIndex: Int! { set get };
 
+  var modalIndexPrev: Int! { set get };
+
   var modalNativeID: String! { set get };
+
 };
 
 /// Contains modal-related properties for keeping track of the state of the

ios/src_library/React Native/RNIModal/RNIModalManager.swift

@@ -35,6 +35,9 @@ public let RNIModalManagerShared = RNIModalManager.sharedInstance;
 ///   window instance, and only updating it based on the modal's associated
 ///   window instance.
 ///
+/// * This can also be fixed by programmatically determining the modal's
+///   `modalIndex`.
+///
 public class RNIModalManager {
 
   // MARK: - Static Properties
@@ -193,7 +196,9 @@ public class RNIModalManager {
     let key = self.createModalNativeID();
 
     modal.modalNativeID = key;
+
     modal.modalIndex = -1;
+    modal.modalIndexPrev = -1;
 
     modal.isModalPresented = false;
     modal.isModalInFocus = false;
@@ -215,9 +220,12 @@ extension RNIModalManager: RNIModalFocusNotifiable {
   public func onModalWillFocusNotification(
     sender modal: RNIModal
   ) {
-    self.currentModalIndex += 1;
+    let nextModalIndex = self.currentModalIndex + 1;
+    self.currentModalIndex = nextModalIndex;
+
+    modal.modalIndexPrev = modal.modalIndex;
+    modal.modalIndex = nextModalIndex;
 
-    modal.modalIndex = self.currentModalIndex;
     modal.onModalWillFocusNotification(sender: modal);
 
     self.modalInstances.forEach {
@@ -251,6 +259,8 @@ extension RNIModalManager: RNIModalFocusNotifiable {
 
   public func onModalWillBlurNotification(sender modal: RNIModal) {
     self.currentModalIndex -= 1;
+
+    modal.modalIndexPrev = modal.modalIndex;
     modal.modalIndex = -1;
 
     modal.onModalWillBlurNotification(sender: modal);

ios/src_library/React Native/RNIModalView/RNIModalView.swift

@@ -36,6 +36,8 @@ class RNIModalView: UIView, RNIModalFocusNotifying, RNIModalIdentity,
   // -------------------------------------
 
   var modalIndex: Int!;
+  var modalIndexPrev: Int!;
+
   var modalNativeID: String!;
 
   // MARK: - Properties - RNIModalState