Output a standalone JSON artifact

[remcomokveld]

The current outputs of the gradle profiler are a CSV file and an HTML file that has JSON embedded into it.

I think it would be a nice enhancement to output that JSON in a separate file instead, and let the html file consume it from there.

Happy to look into opening a PR for this since I understand that y'all might have higher priorities. I just want to avoid putting time into this and then hearing "no we don't want that" 😄