Add detected libraries to the JSON output results

Is your feature request related to a problem? Please describe. PR #21 added support for printing out detected JS libraries and their versions but they are provided if a JSON output is being used --json

[lirantal]

Yep, I agree. Make that change in the structure with your PR and we will mark it as a breaking change when I merge it to master.

[mixth]

Interested. Does this JSON structure look fine to you?

{
  "website": "https://example.com",
  ...
  "libraries": [
    {  "name": "", "version": "" }
  ]
}