dsh-exa-search: Exa Deep Web Search Plugin for DeepSeek Harness

`dsh-exa-search` is an online plugin for DeepSeek Harness (DSH) that enhances the retrieval depth and quality of the existing `web_search` tool by integrating the Exa Search API. It supports multiple search types (such as deep and fast) and allows configuration of the API key, timeout, number of results, and output character limit. It is easy to install and features robust error handling, making it suitable for technical research and academic source discovery. Configuration is recommended via environment variables or the DSH interface, and changes require restarting the profile to take effect.