feat(ios): added event to detect that screenshot was taken (#11665)

Fixes TIMOB-27853

apidoc/Titanium/App/iOS/iOS.yml

@@ -1395,6 +1395,11 @@ events:
     platforms: [iphone, ipad]
     since: "8.2.0"
 
+  - name: screenshotcaptured
+    summary: Fired after the user takes a screenshot, e.g. by pressing both the home and lock screen buttons.
+    platforms: [iphone, ipad]
+    since: "9.1.0"
+
 ---
 name: NotificationParams
 summary: |

iphone/Classes/TiAppiOSProxy.m

@@ -133,6 +133,13 @@ - (void)_listenerAdded:(NSString *)type count:(int)count
                                                  name:kTiTraitCollectionChanged
                                                object:nil];
   }
+
+  if ((count == 1) && [type isEqual:@"screenshotcaptured"]) {
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(didTakeScreenshot:)
+                                                 name:UIApplicationUserDidTakeScreenshotNotification
+                                               object:nil];
+  }
 }
 
 - (void)_listenerRemoved:(NSString *)type count:(int)count
@@ -189,6 +196,9 @@ - (void)_listenerRemoved:(NSString *)type count:(int)count
   if ((count == 1) && [type isEqual:@"traitcollectionchange"]) {
     [[NSNotificationCenter defaultCenter] removeObserver:self name:kTiTraitCollectionChanged object:nil];
   }
+  if ((count == 1) && [type isEqual:@"screenshotcaptured"]) {
+    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationUserDidTakeScreenshotNotification object:nil];
+  }
 }
 
 #pragma mark Public
@@ -205,6 +215,11 @@ - (void)didChangeTraitCollection:(NSNotification *)info
   [self fireEvent:@"traitcollectionchange"];
 }
 
+- (void)didTakeScreenshot:(NSNotification *)info
+{
+  [self fireEvent:@"screenshotcaptured"];
+}
+
 - (void)didReceiveApplicationShortcutNotification:(NSNotification *)info
 {
   NSMutableDictionary *event = [[NSMutableDictionary alloc] initWithDictionary:@{