✨ Improve JSON format

[laurentsimon]

• Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• PR title follows the guidelines defined in https://github.com/ossf/scorecard/blob/main/CONTRIBUTING.md#pr-process

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  feature

• What is the current behavior? (You can also link to an open issue here)
  lack of info in JSON format

• What is the new behavior (if this is a feature change)?

1. JSON format uses lower-case letter for fields (OSV, GitHub API, etc all use lowercase fields)
2. Add scorecard's hash and version to JSON
3. Retrieve version/hash information automatically
4. Move build info under pkg/

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  no

• Other information:

[azeemshaikh38]

Can we decouple logic for cron job JSON from Scorecard JSON before this PR?

[laurentsimon]

Can we decouple logic for cron job JSON from Scorecard JSON before this PR?

I'll start working on it. Are there unit tests needs for the cron job/JSON? I don't see any. I think I'll add JSON unit tests/schema validator as I did for the scorecard JSON format. Sounds good?

[azeemshaikh38]

Can we decouple logic for cron job JSON from Scorecard JSON before this PR?

I'll start working on it. Are there unit tests needs for the cron job/JSON? I don't see any. I think I'll add JSON unit tests/schema validator as I did for the scorecard JSON format. Sounds good?

SGTM

[laurentsimon]

Can we decouple logic for cron job JSON from Scorecard JSON before this PR?

I'll start working on it. Are there unit tests needs for the cron job/JSON? I don't see any. I think I'll add JSON unit tests/schema validator as I did for the scorecard JSON format. Sounds good?

done with #941