Examine source code of VK advanced

{
  "manifest_version": 2,
  "name": "VK advanced",
  "version": "0.3.1",
  "description": "Improves UX on vk.com",
  "icons": {
    "48": "icons/vk-logo.png"
  },
  "applications": {
    "gecko": {
      "id": "VKAdvanced@cretiX",
      "strict_min_version": "60.0"
    }
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/vk-logo.png",
    "default_title": "VK advanced",
    "default_popup": "popup/default_popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://vk.com/*"
      ],
      "js": [
        "default.js"
      ]
    }
  ]
}