chromium/chrome/test/data/extensions/browsertest/proxy_setting_extension/manifest.json

{
    "manifest_version": 3,
    "name": "Proxy extension for testing",
    "version": "1.0.2",
    "background": {
      "service_worker": "background.js"
    },
    "permissions": [
        "proxy", "tabs"
    ],
    "incognito": "spanning"
}