Examine source code of Focus Keeper

{
  "manifest_version": 2,
  "name": "Focus Keeper",
  "version": "1.0",
  "description": "Track and manage the time you spend on websites to improve your productivity.",
  "browser_specific_settings": {
    "gecko": {
      "id": "{3fcb96bb-b010-4bcc-95a1-a99c92ad1a99}",
      "strict_min_version": "120.0"
    }
  },
  "background": {
    "scripts": [
      "background_focus.js"
    ]
  },
  "browser_action": {
    "default_icon": "icon64.png",
    "default_title": "Focus Keeper",
    "default_popup": "popup_focus.html"
  },
  "permissions": [
    "tabs",
    "storage",
    "idle"
  ],
  "icons": {
    "64": "icon64.png",
    "128": "icon128.png"
  }
}