Examine source code of Osu! Beatmaps

{
  "manifest_version": 2,
  "name": "Osu! Beatmaps",
  "version": "2.3.1",
  "description": "List of new and popular Osu! beatmaps.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "index.html"
  },
  "permissions": [
    "https://osu.ppy.sh/*",
    "https://packs.ppy.sh/*",
    "downloads"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "OsuNewMapsExtension@github.com",
      "strict_min_version": "60.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://osu.ppy.sh/"
      ],
      "js": [
        "index.js"
      ]
    }
  ]
}