Added missing sibling methods to QModelIndex

Author: TilmanK

PyQt5-stubs/QtCore.pyi

@@ -1813,6 +1813,8 @@ class QModelIndex(sip.simplewrapper):
     def column(self) -> int: ...
     def row(self) -> int: ...
     def child(self, arow: int, acolumn: int) -> 'QModelIndex': ...
+    def siblingAtColumn(self, column: int) -> 'QModelIndex': ...
+    def siblingAtRow(self, row: int) -> 'QModelIndex': ...
 
 
 class QPersistentModelIndex(sip.simplewrapper):