Add Interactive HTML Preview extension to community catalog (#2585)

Add preview extension submitted by @bigsmartben to:
- extensions/catalog.community.json (alphabetical order)
- docs/community/extensions.md community extensions table

Closes #2578

docs/community/extensions.md

@@ -51,6 +51,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | Fleet Orchestrator | Orchestrate a full feature lifecycle with human-in-the-loop gates across all SpecKit phases | `process` | Read+Write | [spec-kit-fleet](https://github.com/sharathsatish/spec-kit-fleet) |
 | GitHub Issues Integration 1 | Generate spec artifacts from GitHub Issues - import issues, sync updates, and maintain bidirectional traceability | `integration` | Read+Write | [spec-kit-github-issues](https://github.com/Fatima367/spec-kit-github-issues) |
 | GitHub Issues Integration 2 | Creates and syncs local specs from an existing GitHub issue | `integration` | Read+Write | [spec-kit-issue](https://github.com/aaronrsun/spec-kit-issue) |
+| Interactive HTML Preview | Generate self-contained interactive HTML prototypes from Spec Kit artifacts | `docs` | Read+Write | [spec-kit-preview](https://github.com/bigsmartben/spec-kit-preview) |
 | Intelligent Agent Orchestrator | Cross-catalog agent discovery and intelligent prompt-to-command routing | `process` | Read+Write | [spec-kit-orchestrator](https://github.com/pragya247/spec-kit-orchestrator) |
 | Iterate | Iterate on spec documents with a two-phase define-and-apply workflow — refine specs mid-implementation and go straight back to building | `docs` | Read+Write | [spec-kit-iterate](https://github.com/imviancagrace/spec-kit-iterate) |
 | Jira Integration | Create Jira Epics, Stories, and Issues from spec-kit specifications and task breakdowns with configurable hierarchy and custom field support | `integration` | Read+Write | [spec-kit-jira](https://github.com/mbachorik/spec-kit-jira) |