Examine source code of Close Containers

{
  "author": "igorlogius",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {},
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+C"
      }
    }
  },
  "icons": {
    "64": "icon.png"
  },
  "manifest_version": 2,
  "name": "Close Containers",
  "permissions": [
    "cookies",
    "contextualIdentities"
  ],
  "version": "1.0.0",
  "browser_specific_settings": {
    "gecko": {
      "id": "{9195588d-ec71-42c5-9a20-8b1bded4786f}"
    }
  }
}