Examine source code of Close Site Tabs

{
  "manifest_version": 2,
  "name": "Close Site Tabs",
  "version": "1.0",
  "description": "Adds a 'Close site tabs' option to the tab title pop-up menu to close all tabs from the same base domain.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "tabs",
    "menus"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "close-site-tabs@srinryn.com"
    }
  }
}