Examine source code of Neco Arc Buddy

{
  "name": "Neco Arc Buddy",
  "version": "1.0",
  "description": "Added a little dancing Neco Arc and some good music to every website",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "assets/images/neco-arc-dance.gif",
    "assets/music/bgm.ogg"
  ],
  "icons": {
    "16": "icons/icon_16x16.png",
    "48": "icons/icon_48x48.png",
    "128": "icons/icon_128x128.png"
  },
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{da5915b1-78f0-4505-ad3b-a6ac7a316bc0}"
    }
  }
}