dsh-keyword-extract: Keyword Extraction

The `dsh-keyword-extract` plugin for DeepSeek Harness (DSH) provides native keyword extraction capabilities. Built with Node.js and requiring no network dependencies, it supports running locally or in restricted environments. Users can install it using `dsh plugin add github:uckkk/dsh-keyword-extract`; after installation, its tools can be invoked directly in a session to handle long texts or quickly locate core information.