Examine source code of Make me focus mode

{
  "manifest_version": 2,
  "name": "Focus Mode",
  "version": "1.0",
  "description": "Hide all open tabs except the current one to help you focus.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8198fb98-9da9-429e-9979-729f5dc6b019}"
    }
  }
}