Examine source code of Hiroba Extension

{
  "manifest_version": 2,
  "name": "Hiroba Extension",
  "version": "0.3.2",
  "description": "Extension to improve functionality of donderhiroba.jp.",
  "icons": {
    "48": "icons/hiroba-48.png"
  },
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://donderhiroba.jp/*"
      ],
      "js": [
        "js/songlist.js",
        "js/hiroba.js"
      ],
      "css": [
        "css/hiroba.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{44f154ea-4972-417c-95d8-1d72556eeed7}"
    }
  }
}