Examine source code of Battery Monitor

{
  "name": "Battery Monitor",
  "version": "1.5resigned1",
  "description": "Manage the battery level of your device",
  "icons": {
    "128": "icon.png"
  },
  "browser_action": {
    "default_icon": "battery_full.png",
    "default_popup": "popup.html"
  },
  "manifest_version": 2,
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b391b317-c8ab-4f84-8e0d-ef6647f73c16}"
    }
  }
}