Examine source code of Tab Stacker

{
  "manifest_version": 2,
  "name": "Tab Stacker",
  "version": "1.1resigned1",
  "description": "Moves selected unpinned tabs to the left of the tab bar.",
  "permissions": [],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1a25ef8f-9c49-47ee-97fa-925ad0a86652}"
    }
  }
}