Examine source code of FL Time Keeper

{
  "name": "FL Time Keeper",
  "description": "Display convenient reminder when Time the Healer comes.",
  "version": "1.1.1",
  "manifest_version": 2,
  "permissions": [],
  "content_scripts": [
    {
      "matches": [
        "https://www.fallenlondon.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_icon": {
      "16": "/images/fl-time-keeper-icon-16.png",
      "32": "/images/fl-time-keeper-icon-32.png",
      "48": "/images/fl-time-keeper-icon-48.png",
      "128": "/images/fl-time-keeper-icon-128.png"
    }
  },
  "icons": {
    "16": "/images/fl-time-keeper-icon-16.png",
    "32": "/images/fl-time-keeper-icon-32.png",
    "48": "/images/fl-time-keeper-icon-48.png",
    "128": "/images/fl-time-keeper-icon-128.png"
  },
  "web_accessible_resources": [
    "inject.js"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4d38d9d9-d146-42e5-8349-c9676f55dc0e}"
    }
  }
}