Fixed onScroll prop in mulitline TextInput (#23668)

Summary:
We lose the support of `onScroll` prop for multiline TextInput, let's add it again.

[iOS] [Fixed] - Fixed onScroll prop in mulitline TextInput
Pull Request resolved: https://github.com/facebook/react-native/pull/23668

Differential Revision: D14253996

Pulled By: cpojer

fbshipit-source-id: 43ed191e18fdb716f6c53be3bf0f59f917b34b59

Libraries/Text/TextInput/RCTBackedTextInputDelegate.h

@@ -27,6 +27,10 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)textInputDidChangeSelection;
 
+@optional
+
+- (void)scrollViewDidScroll:(UIScrollView *)scrollView;
+
 @end
 
 NS_ASSUME_NONNULL_END

Libraries/Text/TextInput/RCTBackedTextInputDelegateAdapter.m

@@ -213,6 +213,15 @@ static void *TextFieldSelectionObservingContext = &TextFieldSelectionObservingCo
   [self textViewProbablyDidChangeSelection];
 }
 
+#pragma mark - UIScrollViewDelegate
+
+- (void)scrollViewDidScroll:(UIScrollView *)scrollView
+{
+  if ([_backedTextInputView.textInputDelegate respondsToSelector:@selector(scrollViewDidScroll:)]) {
+    [_backedTextInputView.textInputDelegate scrollViewDidScroll:scrollView];
+  }
+}
+
 #pragma mark - Public Interface
 
 - (void)skipNextTextInputDidChangeSelectionEventWithTextRange:(UITextRange *)textRange