Examine source code of DubPlus

{
  "manifest_version": 2,
  "name": "DubPlus",
  "short_name": "Dub+",
  "author": "Dub+ Devs",
  "description": "Dub+ - A Dubtrack.fm and QueUp.net script/extension for added features and customizations",
  "homepage_url": "https://dub.plus/",
  "browser_action": {
    "default_icon": "icons/48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.dubtrack.fm/join/*",
        "*://*.queup.net/join/*"
      ],
      "js": [
        "scripts/loader.js"
      ],
      "run_at": "document_end"
    }
  ],
  "icons": {
    "16": "icons/18.png",
    "19": "icons/19.png",
    "38": "icons/38.png",
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "version": "3.0.0.0"
}