Allow a way for modpacks to add additional blocks that can be part of cleanroom floor/walls

[tomprince]

Cross-mod Integration

e.g. OpenBlocks Elevator, Tranvel Anchors

Feature Description

It you could include things like elevators or travel anchors (perhaps up to a small (2-4) limit) could be included in the floor or walls of a cleanroom. One way to handle this would be to have a block tag of extra blocks that can be included in a cleanroom structure. The tag could either be left blank by default, or populated with elevators/travel anchors from some common mods.