Replace json with orjson

[fdlm]

Python's standard json library can produce invalid JSON files, for example if we serialize nan, +inf or -inf floating point values.

I replaced it with orjson, which is faster and produces compliant JSON files.

One important difference is that orjson serializes to bytes instead of str. I checked with some files, and the results of the old serialization with json and orjson were exactly the same, so I think we're fine.

[richard-vogl]

looks good! I hope these bytes are still UTF-8 😄

[richard-vogl]

looks good! I hope these bytes are still UTF-8 😄

It appears it is UTF-8, just checked...

[alvesfelipe]

$ poetry lock and have fun!