Proposal: Add a "Showcase / Ecosystem" section to README for projects implementing OKF

### Summary

I would like to propose adding an **Ecosystem / Showcase** (or "Built with OKF") section to the `README.md` to highlight open-source tools, servers, and integrations that implement the Open Knowledge Format standard.

### Motivation

As the OKF standard gains traction, showcasing real-world implementations helps newcomers understand practical usage patterns and discover ready-to-use tooling across different agent frameworks.

### Example Submission

To kick off the list, I built [mcp-memory](https://github.com/fellowgeek/mcp-memory), an open-source Model Context Protocol (MCP) server that structures LLM agent memories using OKF while leveraging SQLite FTS5 for fast, local full-text search.

* **Project:** [mcp-memory](https://github.com/fellowgeek/mcp-memory)
* **Description:** MCP server implementing OKF for structured agent memory paired with local SQLite FTS5 search capabilities.

### Proposed Next Steps

If the maintainers are open to this, I would be happy to submit a pull request adding the section to the README along with this initial entry and standard contribution guidelines for others to add their projects.

Start by reviewing README.md to find the appropriate location and formatting for a new Ecosystem / Showcase section. Add the mcp-memory entry and contribution guidance for future projects, then verify the links, descriptions, and README rendering.

Written by the indexing model from the issue text.