Update license format in package.json

[zypA13510]

"licenses" property is deprecated. From https://docs.npmjs.com/files/package.json:

Some old packages used license objects or a “licenses” property containing an array of license objects:

// Not valid metadata
{ "license" :
  { "type" : "ISC"
  , "url" : "https://opensource.org/licenses/ISC"
  }
}

// Not valid metadata
{ "licenses" :
  [
    { "type": "MIT"
    , "url": "https://www.opensource.org/licenses/mit-license.php"
    }
  , { "type": "Apache-2.0"
    , "url": "https://opensource.org/licenses/apache2.0.php"
    }
  ]
}

Those styles are now deprecated. Instead, use SPDX expressions, like this:

{ "license": "ISC" }

{ "license": "(MIT OR Apache-2.0)" }

Closes #266.