Examine source code of Image Resolution Viewer

{
  "manifest_version": 2,
  "name": "Image Resolution Viewer",
  "version": "1.0",
  "description": "Show image resolution on right-click.",
  "permissions": [
    "contextMenus",
    "activeTab"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "96": "icon96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "imageresolution@example.com"
    }
  }
}