Proposal: Parameter to sort the json keys in the exported file

[tilmanschweitzer]

Sadly, the objects returned from Firestore have a random key order than changes with each export. Therefore it would be great to have a parameter like --sort-keys to have a deterministic output. My use-case for a deterministic output is to check the output for changes.

There are libs to produce a stable output, but this one has no typings.

https://github.com/substack/json-stable-stringify