docs: add Open WebUI Community page to Ecosystem

[silentoplayz]

Summary

Adds an Ecosystem page for Open WebUI Community, the platform at openwebui.com, and a line for it on the Ecosystem index. Until now the docs only touched the site from the Community Plugins and chat sharing pages, and nothing explained how it connects to an instance.

The page covers:

• what is on the site and the post types, with where each one lands in Open WebUI when imported
• importing a post with Get, including that the instance only has to open in your browser (the hand-off runs between two tabs, so localhost works)
• the Share buttons in Workspace, Admin Panel > Functions and the chat share dialog
• the two links into the Models catalog's reviews
• syncing usage stats to the Leaderboard, with the full list of what a sync sends and does not send, taken from the export the dialog uses
• what turning off Community Sharing hides

It follows the layout of the other Ecosystem pages, with a banner in the same template as theirs.

Related issue or discussion

Closes #1444

Checklist

• I have reviewed the relevant documentation and matched the existing style.
• This PR meets Open WebUI's contribution standards: it is accurate, relevant to users, narrowly scoped, maintainable, and not promotional content, advertising, lead generation, SEO placement, or a request to list a product, service, provider, integration, gateway, tool, or company primarily for visibility.
• I understand that PRs that do not meet these standards may be closed without review and will not be merged. Repeated, low-quality, off-topic, promotional, or intentionally misleading submissions may result in the contributor being blocked from future participation in Open WebUI repositories.

Notes for reviewers

The Open WebUI side was checked against dev at 015dbc8: the Share handlers and the pages they open, the import listeners on the Models, Prompts, Tools and Functions create pages, SyncStatsModal.svelte, the MessageStats and ChatStatsExport schemas, and every UI element gated by enable_community_sharing. The site side was checked on openwebui.com on 2026-10-01, signed in, without posting, importing or syncing anything: the Get panel (Import, Download as JSON export) and the Leaderboard's Sync dialog (requires v0.7.0+, upload JSON file directly).

The "Turn it off" list names Share in the function menu, which depends on open-webui/open-webui#31820. On current dev, Share in the function menu still shows with Community Sharing off.

The page built and rendered with docusaurus start in light and dark mode, and every internal link and anchor on it resolves.

Light	Dark

[tjbck]

Great starting point, thanks!