Datastore.write not correctly writing zero-indexed array

[dave (Dave Hayden)]

I have a fix for that but it requires using non-standard JSON files with integer keys. Seems to work, but I'd like to get more testing on it before we ship it.

Datastore issue with negative indices

I got this working today but it took some significant changes to the encoder/decoder guts so I'm not comfortable pushing it in the next update. I'll get it merged to main after that so we can have it running here for a while to try and catch the bugs I inevitably added.