Add --json option to outdated command

[carloscuesta]

• I'd be willing to implement this feature (contributing guide)

Describe the user story

As a developer, I want to be able to parse the output returned by the outdated command in a programmatic way. Right now there are only two options, a table and a list.

Describe the solution you'd like

I would like to add a --json option to the outdated command so I can parse the output of it with a script.

Here's an example:

pnpm outdated --json

The following command 👆 should return a JSON with the outdated dependencies in one of the following formats:

[
  {
    "package": "package-name",
    "current": "x.y.z",
    "latest": "x.y.z",
    "dependents": ["dependent-package"]
  }
]

{
  "package-name": {
   "current": "x.y.z",
   "latest": "x.y.z",
   "dependents": ["foo"]
  }
}

Describe the drawbacks of your solution

• We will increase the complexity of the command options a bit.
• We will have to maintain 3 different output formats.

Describe alternatives you've considered

• Using the --no-table option and then parsing the output, but it's not ideal as it requires much more effort to parse the output.

[carloscuesta]

Duplicate of #2705 looks like this landed in 7.15

https://github.com/pnpm/pnpm/releases/tag/v7.15.0

Thanks! ❤️