Examine source code of Environment switcher

{
  "manifest_version": 3,
  "name": "Environment switcher",
  "short_name": "Env switcher",
  "version": "0.2",
  "version_name": "0.2 Beta",
  "author": "Sander den Hollander",
  "homepage_url": "https://github.com/NickMous/Environment-Switcher",
  "developer": {
    "name": "NickMous",
    "url": "https://nickmous.com"
  },
  "omnibox": {
    "keyword": "env"
  },
  "description": "Switch between different environments with a click of a button",
  "permissions": [
    "tabs",
    "activeTab",
    "storage",
    "scripting"
  ],
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": "icons/icon.png",
    "default_title": "Environment switcher"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "node_modules/webextension-polyfill/dist/browser-polyfill.js",
        "content_scripts/changeEnv.js"
      ]
    }
  ],
  "options_ui": {
    "page": "settings/settings.html",
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "envswitcher@nickmous.com"
    }
  }
}