Examine source code of Freemium

{
  "manifest_version": 2,
  "name": "Freemium",
  "version": "0.1.2resigned1",
  "description": "Remove premium articles from Medium",
  "icons": {
    "48": "icons/48x48.png",
    "96": "icons/96x96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://medium.com/*"
      ],
      "js": [
        "main.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{295e2965-eddf-4429-b1e4-c3332f1b9c64}"
    }
  }
}