Examine source code of Three Island

{
  "name": "Three Island",
  "version": "1.6.8",
  "manifest_version": 2,
  "description": "A Firefox extension for Pokémon Showdown that offers a seamless Poképaste experience.",
  "homepage_url": "https://github.com/PartMan7/Three-Island",
  "icons": {
    "48": "icons/three-island-48.png",
    "96": "icons/three-island-96.png",
    "128": "icons/three-island-128.png"
  },
  "permissions": [
    "storage",
    "*://play.pokemonshowdown.com/*",
    "*://*.psim.us/*",
    "*://pokepast.es/**",
    "*://crob.at/**"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://play.pokemonshowdown.com/*",
        "*://*.psim.us/*"
      ],
      "js": [
        "three-island.js"
      ]
    }
  ],
  "browser_action": {
    "default_icon": "icons/three-island-48.png",
    "default_title": "Three Island",
    "default_popup": "popup/popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8cf2534c-9c6c-6ec3-526b-d9a154f042f2}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}