fix(ios): make programmatically focus work on iOS 13 (#438)

closes #435

Author: jcesarmobile

src/ios/CDVWKWebViewEngine.m

@@ -322,9 +322,12 @@ - (void) keyboardDisplayDoesNotRequireUserAction {
     Class class = NSClassFromString(@"WKContentView");
     NSOperatingSystemVersion iOS_11_3_0 = (NSOperatingSystemVersion){11, 3, 0};
     NSOperatingSystemVersion iOS_12_2_0 = (NSOperatingSystemVersion){12, 2, 0};
+    NSOperatingSystemVersion iOS_13_0_0 = (NSOperatingSystemVersion){13, 0, 0};
     char * methodSignature = "_startAssistingNode:userIsInteracting:blurPreviousNode:changingActivityState:userObject:";
 
-    if ([[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion: iOS_12_2_0]) {
+    if ([[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion: iOS_13_0_0]) {
+         methodSignature = "_elementDidFocus:userIsInteracting:blurPreviousNode:activityStateChanges:userObject:";
+     } else if ([[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion: iOS_12_2_0]) {
         methodSignature = "_elementDidFocus:userIsInteracting:blurPreviousNode:changingActivityState:userObject:";
     }