Examine source code of openUR

{
  "manifest_version": 2,
  "name": "openUR",
  "version": "1.4",
  "description": "This extension helps you to save the webpages. The saved webpage links can be opened one at a time or can be opened all at once.",
  "homepage_url": "https://github.com/va6un/openUR-firefox",
  "icons": {
    "32": "icons/openur-32.png",
    "48": "icons/openur-48.png",
    "96": "icons/openur-96.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/openur-48.png",
    "default_title": "openUR - open/save your favorite webpages",
    "default_popup": "popup/index.html",
    "browser_style": true
  }
}