Allow JSON stringified buffers to be converted to Buffer when serializing

[extremeheat]

Needed for PrismarineJS/bedrock-protocol#83, allows serializing previously JSON.stringified packets.

[KaffinPX]

LGTM

[rom1504]

Why can't you convert to buffer in the user code ?

[extremeheat]

In the tests,

• the packets are serialized to JSON after parsing
• written to disk
• read from disk, JSON.parse'd
• piped back to createPacketBuffer without any changes

It's possible to convert to buffer, but that would mean recursively walking through the objects then creating Buffer instances out of them. So there would have to be an intermediate parsing step before, with knowledge of the schema.

[rom1504]

Ok, can you make the same change in the interpreter ?

[extremeheat]

done