Examine source code of ImageHelper

{
  "manifest_version": 2,
  "name": "ImageHelper",
  "version": "1.0",
  "description": "Adds two buttons for image downloads",
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "exclude_matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "browser_action": {
    "default_icon": {
      "16": "icon-16.png",
      "32": "icon-32.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{93ba5fa6-03f3-4a48-aa08-0518aac4760d}"
    }
  }
}