Proposal: add a "Community & ecosystem tools" section to the README

Hi! Opening this as a proposal — happy to send the PR if you're open to it.

Since OKF shipped, a number of open-source community tools have appeared around
the format: visual editors, Claude Code skills, linters/validators, CLIs, and
publishers. There's currently no place in the repo that points people to them,
and newcomers keep asking "what can I use to author or validate OKF?"

**Proposal:** add a short **Community & ecosystem tools** section to the README
(or a `COMMUNITY.md`) that links them — name + one line each, matching the repo's style.
Draft below.

Totally open on the inclusion bar — set whatever criteria you prefer and I'll trim to match.

Now they are sorted by github stars desc.

--- draft ---

## Community & ecosystem tools

Open-source tools built by the community around OKF:

**Editors**
- [OWOX Model Canvas](https://github.com/OWOX/owox-model-canvas) — visual canvas / ERD editor; imports & exports OKF v0.1 (opens the GA4, Stack Overflow and Bitcoin samples). Apache-2.0, free live demo.
- [OnyxWriter](https://github.com/activetwist/OnyxWriter) — local-first desktop editor for OKF bundles.

**Agent skills & toolkits**
- [okf-knowledge](https://github.com/sniperunder123/okf-knowledge) — a `/okf` Claude Code skill to create, read, maintain and visualize bundles.
- [okf-skills](https://github.com/scaccogatto/okf-skills) — Claude Code toolkit to author, maintain, validate and visualize OKF.
- [okf-frontmatter](https://github.com/longsizhuo/okf-frontmatter) — skill to keep repo docs under OKF with fast doc/schema lookup.

**Validation & linting**
- [okf-conformance](https://github.com/Sudhakaran88/okf-conformance) — checks whether a bundle conforms to the spec.
- [okf-lint](https://github.com/thisismydesign/okf-lint) — a linter for OKF.

**CLI**
- [openknowledge](https://github.com/openknowledge-sh/openknowledge) — CLI for managing OKF bundles.

**Generation & publishing**
- [OKFy](https://github.com/0dust/OKFy) — turns existing docs into agent-readable OKF bundles.
- [kiso](https://github.com/oak-invest/kiso) — publishing engine that turns OKF bundles into sites.

--- end draft ---

Disclosure: I contribute to OWOX Model Canvas (one of the editors above).
However, it's not created to be paid. Just a free tool from the community to the community.
The intent is a neutral, useful index for the whole community — happy to hand the list and its criteria to a maintainer.

Start by comparing the README's existing organization and link style, then review the proposed list and decide whether it belongs in the README or a new COMMUNITY.md. Done means adding a neutral, concise Community & ecosystem tools section with the agreed inclusion criteria and links, while matching the repository's style.

Written by the indexing model from the issue text.