Examine source code of Snap -> Share

{
  "manifest_version": 2,
  "name": "Snap -> Share",
  "version": "1.0",
  "description": "Quickly generate a QR code to share the current URL of your activeTab",
  "browser_specific_settings": {
    "gecko": {
      "id": "admin@larsson.wtf"
    }
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icons/icon48.png",
      "96": "icons/icon96.png"
    },
    "default_title": "Snap -> Share"
  },
  "permissions": [
    "activeTab"
  ]
}