Saving heightmap information from map_chunk

[TreeOfSelf]

https://minecraft.gamepedia.com/Chunk_format

Reading through the chunk format I see there is important heightmap information. I do not think it is saved in versions prior to when you would have to manually parse it from the data. I sadly am not well equipped to do it, because I am not good with working with raw data as a javascript programmer.
Right now for one of my mineflayer projects I am shooting rays down from the sky (while loop until hit) and it is quite expensive. It would be extremely handy for me to have this heightmap information. Just a consideration.

[rom1504]

yeah we could propagate it here indeed