Examine source code of Open in All Containers

{
  "manifest_version": 2,
  "name": "Open in All Containers",
  "version": "1.0",
  "description": "Right-click a link or bookmark and open it in all accessible Firefox containers",
  "permissions": [
    "contextMenus",
    "tabs",
    "bookmarks",
    "contextualIdentities",
    "cookies"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e2049331-0974-4a0a-bdc5-e97127784197}"
    }
  }
}