Add conda-deny check --json

[pavelzw]

It might be nice to also have json output for the check. Maybe something like this

$ conda-deny check --json
{
  "unsafe": [
    "ghp-import-2.1.0-pyhd8ed1ab_0": {
      "platform": "noarch",
      "license": "LicenseRef-Tumbolia-Public",
      "environments": ["default", "lint"],
    }, ...
    "gpgme-1.18.0-h27087fc_0": {
      "platform": "linux-64",
      "license": "GPL-2.1-or-later AND LGPL-2.1-or-later AND MIT",
      "environments": ["default", "lint"],
      "non-spdx": true
    },
    // ...
  ],
  "safe": // ...
}