Examine source code of Key Master

{
  "name": "Key Master",
  "short_name": "KeyM",
  "description": "Key Master is an on page key price checker for the Steam store supporting G2Play, G2A and Kinguin",
  "version": "1.1.1resigned1",
  "manifest_version": 2,
  "applications": {
    "gecko": {
      "id": "keymaster@downstairs.be"
    }
  },
  "icons": {
    "16": "icons/rect16.png",
    "48": "icons/rect48.png",
    "128": "icons/rect128.png"
  },
  "background": {
    "scripts": [
      "js/background.js"
    ]
  },
  "permissions": [
    "tabs",
    "https://*/*",
    "http://*/*",
    "https://g2api.downstairs.be/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://store.steampowered.com/app/*",
        "https://store.steampowered.com/app/*, http://www.g2play.net/category/*"
      ],
      "css": [
        "css/btn.css"
      ],
      "js": [
        "js/currsymbols.js",
        "js/jquery.min.js",
        "js/g2req.js"
      ]
    }
  ]
}