Examine source code of CSSOverride

{
  "manifest_version": 2,
  "name": "CSSOverride",
  "version": "3.5",
  "description": "Override any site's CSS with your own rules — saved per domain",
  "browser_specific_settings": {
    "gecko": {
      "id": "{798d5766-b90f-4c4d-b993-a184a84d748a}",
      "strict_min_version": "96.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "16": "img/icon-16.png",
    "32": "img/icon-32.png",
    "48": "img/icon-48.png",
    "96": "img/icon-96.png",
    "128": "img/icon-128.png"
  },
  "browser_action": {
    "default_popup": "ui/widget.html",
    "default_icon": {
      "16": "img/icon-16.png",
      "32": "img/icon-32.png",
      "48": "img/icon-48.png",
      "96": "img/icon-96.png",
      "128": "img/icon-128.png"
    }
  },
  "background": {
    "scripts": [
      "service/tracker.js"
    ]
  },
  "permissions": [
    "tabs",
    "activeTab",
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "css_injector.js"
      ],
      "run_at": "document_idle"
    }
  ]
}