nmp/protodef support for mcpe

[rom1504]

For this we'd need :

• the protocol packets, see MCPE support minecraft-data#65
• a way to build mcpe pipeline (probably just a serialization transform stream) : something like https://github.com/wankdanker/node-datagram-stream or https://github.com/wanderview/node-udp-stream might be useful

(this is completely long-term)

[rom1504]

happening in pocket-minecraft-protocol.
Hopefully we can merge it to nmp at some point.

[rom1504]

https://github.com/NukkitX/Protocol/tree/master/bedrock/bedrock-common/src/main/java/com/nukkitx/protocol/bedrock recent stuff