chromium/chrome/test/data/extensions/blocked_actions/content_script_at_idle/manifest.json

{
  "name": "Blocked Actions Doc Idle",
  "description": "An extension that wants to run at document idle on all urls.",
  "version": "0.1",
  "manifest_version": 3,
  "content_scripts": [{
    "matches": ["<all_urls>"],
    "run_at": "document_idle",
    "js": ["script.js"]
  }]
}