default void notifyCorner(int r) {
        BlockPos pos = posOfCorner(r);
        level().neighborChanged(pos, tile().getBlockState().getBlock(), pos);
    }
Tries to locate a corner connectable part towards r and establish a connection.

@param r The rotation towards the external corner part
@return True if connection was established
core/src/main/java/mrtjp/projectred/core/part/IConnectableFacePart.java