chromium/chrome/test/data/extensions/api_test/tabs/send_message/manifest.json

{
  "name": "chrome.tabs.sendMessage test",
  "version": "0.1",
  "manifest_version": 3,
  "description": "end-to-end browser test for chrome.tabs.sendMessage API",
  "background": {
    "service_worker": "worker.js",
    "type": "module"
  },
  "content_scripts": [
    {
      "matches": ["http://*/*"],
      "js": ["echo.js"],
      "run_at": "document_start"
    }
  ]
}