You can now mine a spawner, get the spawner with a "blank" spawn egg, change its type, and then place that spawner and change its mob type by right clicking the spawner with the spawn egg.
Remember the blank egg and item has to be thrown in the cauldron and only make 1 egg at a time.
All items need for each egg is shown below.
This is part of the Dungeon Derps Datapack Suite.