ol-ext: Undo/redo custom

ol/interaction/UndoRedo is an interaction to handle undo/redo on a map.

This example shows how to use the define() method to define a custom action.

• The push() method lets you push a custom action in the undo list.
• You can use the blockStart() / blockEnd() methods to stack many actions in one undo.

For undoing features properties, look at the undo/redo attributes exmaple.
For more information on UndoRedo interaction look at this example.