Examine source code of Video Seek Mousewheel

{
  "manifest_version": 2,
  "name": "Video Seek Mousewheel",
  "description": "Seek (forward/backward) videos by mouse wheel horizantal scroll in video sites. ex: youtube and twitch",
  "version": "1.0",
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*",
        "*://www.twitch.tv/*",
        "*://player.twitch.tv/*"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "video-seek-mousewheel.js"
  ],
  "icons": {
    "128": "mouse.png"
  },
  "applications": {
    "gecko": {
      "id": "sarim2005@gmail.com",
      "strict_min_version": "42.0"
    }
  }
}