Examine source code of Custom Rule Tester

{
  "name": "__MSG_extensionName__",
  "version": "11.0.0",
  "description": "__MSG_extensionDescription__",
  "developer": {
    "name": "eight04",
    "url": "https://github.com/eight04"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [],
      "run_at": "document_start"
    }
  ],
  "default_locale": "en",
  "manifest_version": 2,
  "options_ui": {
    "page": "options.html"
  },
  "browser_action": {
    "default_icon": "icon.svg",
    "default_title": "__MSG_extensionOptions__",
    "theme_icons": [
      {
        "dark": "icon.svg",
        "light": "icon-light.svg",
        "size": 32
      }
    ]
  },
  "background": {
    "scripts": []
  },
  "permissions": [
    "storage",
    "activeTab"
  ],
  "applications": {
    "gecko": {
      "strict_min_version": "52.0",
      "id": "{45f9f4a3-9918-4a74-9e4d-2019731e924a}"
    }
  }
}