Add Compression for proof output files via gz compression stream api

[James-Oswald]

Files are BIG, make them small. Use .json.gz file extension.

https://developer.mozilla.org/en-US/docs/Web/API/Compression_Streams_API

[RyanR712]

In addition to this, as discussed on 12/15, tracking only the changes made to a JSON from step to step may compress file sizes further. The .gzip solution seems easiest however

Diff solution mentioned in #317 just now