Examine source code of Screen Capture Tool

{
  "manifest_version": 2,
  "name": "Screen Capture Tool",
  "version": "1.0",
  "description": "Select an area and capture a screenshot directly in Firefox.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "downloads",
    "storage"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Capture Screenshot",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "web_accessible_resources": [
    "background.js"
  ],
  "licenses": "MIT",
  "browser_specific_settings": {
    "gecko": {
      "id": "{42d5e503-3dcb-4927-9838-ff3c0783622a}"
    }
  }
}