Examine source code of VK player

{
  "manifest_version": 2,
  "version": "1.0.1",
  "name": "VK player",
  "description": "Adds VK player to the toolbar",
  "browser_specific_settings": {
    "gecko": {
      "id": "dvlad2623@gmail.com",
      "strict_min_version": "45.0"
    }
  },
  "permissions": [
    "tabs",
    "*://*.vk.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.vk.com/*"
      ]
    }
  ],
  "browser_action": {
    "default_icon": {
      "16": "images/icons/16.png",
      "32": "images/icons/32.png",
      "64": "images/icons/64.png"
    },
    "default_title": "VK player",
    "default_popup": "markup.html"
  }
}