xby-domain-lookup: DeepSeek Harness Domain Lookup Plugin

`xby-domain-lookup` is a plugin for DeepSeek Harness (DSH) designed to streamline the domain lookup process for agents. It is maintained by `xby-skill` and provides standard information on domain registration details, name servers, and contacts. Core features include setting a persistent API key (`set_xby_apikey`) and performing lookups using the RDAP/WHOIS protocol (`domain_lookup`). Users need to register on the official website to obtain a key and configure it in the conversation; the plugin supports installation from the official repository and runs with the current process's permissions.