Examine source code of Fast Theme Switcher

{
  "manifest_version": 2,
  "version": "1.5",
  "name": "Fast Theme Switcher",
  "description": "Switch between light/dark theme",
  "homepage_url": "https://github.com/janstuemmel/theme-switcher",
  "browser_action": {
    "default_title": "Fast Theme Switcher",
    "default_popup": "popup.html",
    "browser_style": true,
    "default_icon": {
      "128": "icon.svg"
    }
  },
  "permissions": [
    "management",
    "storage"
  ],
  "icons": {
    "48": "icon.svg",
    "96": "icon.svg",
    "128": "icon.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "theme-switcher@janstuemmel.github.io",
      "strict_min_version": "57.0"
    }
  }
}