docs: add systemprompt-template to Built with rmcp (#820)

Author: Ejb503

README.md

@@ -990,6 +990,7 @@ See [Oauth_support](docs/OAUTH_SUPPORT.md) for details.
 - [hyper-mcp](https://github.com/hyper-mcp-rs/hyper-mcp) - A fast, secure MCP server that extends its capabilities through WebAssembly (WASM) plugins
 - [rudof-mcp](https://github.com/rudof-project/rudof/tree/master/rudof_mcp) - RDF validation and data processing MCP server with ShEx/SHACL validation, SPARQL queries, and format conversion. Supports stdio and streamable HTTP transports with full MCP capabilities (tools, prompts, resources, logging, completions, tasks)
 - [McpMux](https://github.com/mcpmux/mcp-mux) - Desktop app to configure MCP servers once at McpMux, connect every AI client (Cursor, Claude Desktop, VS Code, Windsurf) through a single encrypted local gateway with Spaces for project organization, FeatureSets to switch toolsets per client, and a built-in server registry
+- [systemprompt-template](https://github.com/systempromptio/systemprompt-template) - Single-binary Rust runtime providing MCP governance — authentication, authorisation, rate-limiting, audit trails, and cost tracking for AI agents. Self-hosted, air-gap capable, 3,300+ req/s with sub-5ms governance overhead
 
 
 ## Development