flagsmith-cli export to avoid escaping nested json in multiline flag configs

### Is your feature request related to a problem?

Yes, I want to make my environment config exports be directly diffable between environments without need for post processing expansion of nested json and other multiline strings.

### Describe the solution you'd like.

Have an option in the flagsmith cli tool to expand nested json to be part of the files lines rather than condensed to the json escaped multi "\n" encoded thing we find presently.

### Describe alternatives you've considered

I post process the file in python to do the multi line expansion, or just a crude `sed s/\\\\n/\n/g` to break out whatever values I can to their own line to make the diffs readable.

### Additional context

In order to facilitate arbitrary config diffs it would be convenient to have the flagsmith CLI have an option to permit the user to take nested json flag configs and rather than collapsing them to a single line value do the pretty print expansion in the output file itself. This may be schema breaking but it will also make diffs segregated to their own lines to make spotting inconsistencies a breeze.

This would bias the user to only do json valued configs, which for this benefit I think would be acceptable.