Examine source code of Libby's Close Other Tabs

{
  "applications": {
    "gecko": {
      "strict_min_version": "53.0"
    }
  },
  "description": "Close Other Tabs",
  "manifest_version": 2,
  "name": "Close Other Tabs",
  "version": "1.0.1",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "contextMenus"
  ]
}