Examine source code of Focus Mode

{
  "manifest_version": 2,
  "name": "Focus Mode",
  "version": "1.0",
  "description": "A simple extension to focus on the main content.",
  "permissions": [
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Focus Mode"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c602a37f-9eab-40a5-b643-cceceff90132}"
    }
  }
}