Examine source code of SteamDJ

{
  "manifest_version": 2,
  "name": "SteamDJ",
  "version": "1.1",
  "description": "Change your nickname steam",
  "icons": {
    "48": "icons/Steamdj-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://music.yandex.ru/*",
        "https://steamcommunity.com/*"
      ],
      "js": [
        "steamdj.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/Steamdj-48.png",
    "default_title": "SteamDJ",
    "default_popup": "popup/sdj.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3bed64ce-edad-4b7c-8f92-96355a23a6d8}"
    }
  }
}