Examine source code of Hide Images

{
  "description": "Blocks all images on webpage",
  "manifest_version": 2,
  "name": "block-images",
  "version": "1.1resigned1",
  "icons": {
    "48": "icons/block-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/block-disabled-48.png",
    "default_title": "Block images",
    "browser_style": true
  },
  "permissions": [
    "activeTab",
    "tabs",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b03df290-99ef-4d41-aad5-8939ef084fbe}"
    }
  }
}