Examine source code of FL Duly Noted

{
  "name": "FL Duly Noted",
  "description": "Leave notes on storylet branches in Fallen London.",
  "version": "1.0.3",
  "manifest_version": 2,
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://www.fallenlondon.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_action": {
    "default_icon": {
      "16": "/images/fl-duly-noted-icon-16.png",
      "32": "/images/fl-duly-noted-icon-32.png",
      "48": "/images/fl-duly-noted-icon-48.png",
      "128": "/images/fl-duly-noted-icon-128.png"
    }
  },
  "icons": {
    "16": "/images/fl-duly-noted-icon-16.png",
    "32": "/images/fl-duly-noted-icon-32.png",
    "48": "/images/fl-duly-noted-icon-48.png",
    "128": "/images/fl-duly-noted-icon-128.png"
  },
  "web_accessible_resources": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{20129fe3-b91f-4514-8746-d81ccd7ecf93}"
    }
  }
}