Renewable sponges

Make sponges farmeable, so they can be obtained not my a drop of a mob, but with some mechanic that allows sponges to multiply.

For instance, make them so if they are placed over a magma block on a warm ocean near coral blocks, the sponge would spread replacing those coral blocks by sponges.

The important part of this suggestion is not the method but how actually it can be farmed. Please do not make them a drop of some mob, but introduce a technique so that they the community can make farms that include conveyer belts and other machines, rather than a spawn surface and a killing chamber to obtain the item.

Support to this suggestion is welcomed!