Examine source code of Clocks

{
  "name": "Clocks",
  "version": "1.2",
  "description": "Clocks for Firefox - Analog, Digital, Alarm, Countdows ...",
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "54.0a1"
    }
  },
  "sidebar_action": {
    "default_icon": "icons/icon.svg",
    "default_title": "Clocks",
    "default_panel": "sidebar/panel.html"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "commands": {
    "_execute_sidebar_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+R"
      }
    }
  }
}