fix: #1973 Using the mouse to highlight text very easy to miss the first letter

frontend/appflowy_flutter/packages/appflowy_editor/lib/src/service/selection_service.dart

@@ -348,7 +348,7 @@ class _AppFlowySelectionState extends State<AppFlowySelection>
   void _onPanStart(DragStartDetails details) {
     clearSelection();
 
-    _panStartOffset = details.globalPosition;
+    _panStartOffset = details.globalPosition.translate(-5.0, 0);
     _panStartScrollDy = editorState.service.scrollService?.dy;
 
     _enableInteraction();