Examine source code of Opus UI DevTools

{
  "manifest_version": 2,
  "name": "Opus DevTools",
  "version": "1.2.3",
  "permissions": [
    "activeTab",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "devtools_page": "devtools/devtools.html",
  "icons": {
    "48": "favicon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{857afe45-4521-49cf-a5fe-b20820861d5c}"
    }
  }
}