Examine source code of Visual Bell

{
  "manifest_version": 2,
  "version": "0.1.0",
  "name": "Visual Bell",
  "description": "Make a selected area blink when changes are made.",
  "permissions": [
    "activeTab"
  ],
  "icons": {
    "16": "data/icons/bell.svg",
    "32": "data/icons/bell.svg",
    "48": "data/icons/bell.svg",
    "64": "data/icons/bell.svg",
    "128": "data/icons/bell.svg",
    "256": "data/icons/bell.svg",
    "512": "data/icons/bell.svg"
  },
  "background": {
    "persistent": true,
    "scripts": [
      "background.js"
    ]
  },
  "homepage_url": "https://github.com/nbp/visual-bell/",
  "browser_action": {
    "default_title": "Turn on visual bell on a given area."
  },
  "web_accessible_resources": [
    "data/window/index.html"
  ],
  "commands": {
    "_execute_browser_action": {}
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "visual.bell2@nbp.name",
      "strict_min_version": "90.0"
    }
  }
}