Examine source code of PageProofer

{
  "manifest_version": 2,
  "name": "PageProofer",
  "description": "The easiset way to leave feedback and track issues right on your website.",
  "version": "1.0.3",
  "icons": {
    "128": "icon_128.png"
  },
  "browser_action": {
    "default_icon": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "embed.js"
      ],
      "run_at": "document_end"
    }
  ]
}