Add superpowers-bridge community extension (#2309)

* Add superpowers-bridge community extension

Adds the superpowers-bridge extension by WangX0111 to the community
catalog and README table. This extension bridges spec-kit with
obra/superpowers (brainstorming, TDD, subagent-driven-development,
code-review) into a unified, resumable workflow with graceful
degradation and session progress tracking.

Extension details:
- ID: superpowers-bridge
- Repository: https://github.com/WangX0111/superspec
- Version: 1.0.0
- Commands: 5, Hooks: 3
- License: MIT

* Address Copilot review feedback

- Update top-level updated_at to 2026-04-22
- Shorten description to under 200 characters

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Co-authored-by: 乘浩 <wch453799@alibaba-inc.com>