Examine source code of Tab Counter Mini

{
  "name": "Tab Counter",
  "short_name": "Tab Counter",
  "author": "turquoise-turtle",
  "developer": {
    "name": "turquoise-turtle",
    "url": "https://github.com/turquoise-turtle"
  },
  "version": "0.5.1",
  "description": "A button badge that shows the number of tabs open in a window",
  "homepage_url": "https://github.com/turquoise-turtle/tab-counter-mini",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "id": "tab-counter@techniko.addons.mozilla.org",
      "strict_min_version": "63.0"
    },
    "gecko_android": {
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "strict_min_version": "120.0"
    }
  },
  "icons": {
    "16": "icons/tabcounter-logo-16.png",
    "32": "icons/tabcounter-logo-32.png",
    "64": "icons/tabcounter-logo-64.png",
    "128": "icons/tabcounter-logo-128.png"
  },
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "browser_style": true,
    "default_area": "navbar",
    "default_icon": "icons/tabcounter.plain.min.svg",
    "theme_icons": [
      {
        "dark": "icons/tabcounter-gray10.plain.min.svg",
        "light": "icons/tabcounter-gray90.plain.min.svg",
        "size": 1
      }
    ],
    "default_popup": "popup.html",
    "default_title": "Tab Counter"
  },
  "options_ui": {
    "page": "options.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  }
}