Examine source code of Open…

{
  "manifest_version": 2,
  "name": "Open…",
  "version": "1.0.4",
  "description": "Open any file URL (link or text) with Kitware online viewers such as Glance, VolView or with desktop 3D Slicer with a right click",
  "author": "julien.finet@kitware.com",
  "homepage_url": "https://github.com/KitwareMedical/OpenInBrowserExtension",
  "icons": {
    "16": "images/kitware-16.png",
    "32": "images/kitware-32.png",
    "48": "images/kitware-48.png",
    "128": "images/kitware-128.png"
  },
  "permissions": [
    "contextMenus",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "scripts/background.js"
    ],
    "persistent": false
  },
  "options_ui": {
    "page": "options.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2fb6b7aa-2ac1-45cf-b8b1-153602939cd9}"
    }
  }
}