Examine source code of Focus Guard

{
  "manifest_version": 2,
  "name": "Focus Guard",
  "version": "1.0",
  "description": "Detects frequent tab switching and reminds the user to stay focused.",
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{aa88d83e-d842-4c88-9254-9423fadd8b3f}"
    }
  }
}