Examine source code of Links

{
  "manifest_version": 2,
  "name": "Links",
  "version": "0.1.2",
  "author": "Alexander Karelas",
  "description": "A toolbar button to send the current tab's URL to the links.karelcom.net social bookmarks website.",
  "icons": {
    "48": "icons/icons8-link-48.png",
    "96": "icons/icons8-link-96.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/icons8-link-32.png",
    "default_title": "Links",
    "default_popup": "popup/links.html"
  }
}