Examine source code of Domain Swapper

{
  "icons": {
    "16": "icon16.plasmo.2577fc03.png",
    "32": "icon32.plasmo.d583dc1e.png",
    "48": "icon48.plasmo.e0fcfb1d.png",
    "64": "icon64.plasmo.e6259081.png",
    "128": "icon128.plasmo.96a1ede9.png"
  },
  "manifest_version": 3,
  "action": {
    "default_icon": {
      "16": "icon16.plasmo.2577fc03.png",
      "32": "icon32.plasmo.d583dc1e.png",
      "48": "icon48.plasmo.e0fcfb1d.png",
      "64": "icon64.plasmo.e6259081.png",
      "128": "icon128.plasmo.96a1ede9.png"
    },
    "default_popup": "popup.html"
  },
  "version": "2.0.1",
  "author": "Adam Norwood <adam@adamnorwood.com>",
  "name": "Domain Swapper",
  "description": "Browser extension to allow swapping between hostnames quickly while preserving the rest of the URL ",
  "background": {
    "scripts": [
      "static/background/index.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5ae60257-37eb-451f-ba4f-d37dbf6fa5c9}"
    }
  }
}