added dragOffsetNotifier explanation

Author: mtallenca

lib/src/editor/raw_editor/raw_editor.dart

@@ -25,6 +25,25 @@ class QuillRawEditor extends StatefulWidget {
 
   final QuillController controller;
   final QuillRawEditorConfig config;
+
+  /// dragOffsetNotifier - Only used on iOS and Android
+  ///
+  /// [QuillRawEditor] contains a gesture detector [EditorTextSelectionGestureDetector]
+  /// within it's widget tree that includes a [RawMagnifier]. The RawMagnifier needs
+  /// the current position of selection drag events in order to display the magnifier
+  /// in the correct location. Setting the position to null will hide the magnifier.
+  ///
+  /// Initial selection events are posted by [EditorTextSelectionGestureDetector]. Once
+  /// a selection has been created, dragging the selection handles happens in
+  /// [EditorTextSelectionOverlay].
+  ///
+  /// Both [EditorTextSelectionGestureDetector] and [EditorTextSelectionOverlay] will update
+  /// the value of the dragOffsetNotifier.
+  ///
+  /// The [EditorTextSelectionGestureDetector] will use the value to display the magnifier in
+  /// the correct location (or hide the magnifier if null). [EditorTextSelectionOverlay] will
+  /// use the value of the dragOffsetNotifier to hide the context menu when the magnifier is
+  /// displayed and show the context menu when dragging is complete.
   final ValueNotifier<Offset?>? dragOffsetNotifier;
 
   @override