Examine source code of FL Masquerade

{
  "name": "FL Masquerade",
  "description": "Manage multiple identities in \"Fallen London\" browser game.",
  "version": "1.1.1",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "tabs",
    "storage",
    "alarms",
    "https://api.fallenlondon.com/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.fallenlondon.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "inject.js"
  ],
  "icons": {
    "16": "/images/masks-icon-16.png",
    "32": "/images/masks-icon-32.png",
    "48": "/images/masks-icon-48.png",
    "128": "/images/masks-icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9a90763a-b8ee-4af4-8bc8-2e2989ad5e4d}"
    }
  }
}