Examine source code of breadcrumbus

{
  "description": "Break current tab URLs into navigable breadcrumbs",
  "icons": {
    "16": "resources/themes/original/icon-16.png",
    "32": "resources/themes/original/icon-32.png",
    "64": "resources/themes/original/icon-64.png"
  },
  "homepage_url": "https://github.com/jokokko/breadcrumbus",
  "manifest_version": 3,
  "name": "breadcrumbus",
  "default_locale": "en",
  "options_ui": {
    "page": "options.html",
    "browser_style": false
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "tabs",
    "storage",
    "cookies"
  ],
  "action": {
    "default_icon": {
      "16": "resources/themes/original/icon-16.png",
      "32": "resources/themes/original/icon-32.png"
    },
    "default_title": "Breadcrumbus",
    "default_popup": "tabpanel.html"
  },
  "page_action": {
    "show_matches": [
      "<all_urls>"
    ],
    "default_icon": {
      "32": "resources/themes/original/icon-32-bw.png"
    },
    "default_title": "Breadcrumbus",
    "default_popup": "tabpanel.html"
  },
  "commands": {
    "_execute_action": {
      "suggested_key": {
        "default": "Ctrl+Comma"
      }
    }
  },
  "version": "2.1.1",
  "browser_specific_settings": {
    "gecko": {
      "id": "@breadcrumbus"
    }
  }
}