Add Skills for Fabric to the catalog

[gronnerup]

Summary

Adds Skills for Fabric, Microsoft's official collection of AI agent skills and MCP servers for operating over Microsoft Fabric from CLI/VS Code/Claude, to the catalog. Submitted via issue #23.

Changes

• New catalog entry src/content/tools/skills-for-fabric.md:
  • Category: ai-mcp · Type: library
  • Source: open-source (MIT) · Maintainer: microsoft · Pricing: free · Status: ga
  • Visit → github.com/microsoft/skills-for-fabric, Docs → Microsoft Learn overview

Verification

• npm run build passes (build clean).

Notes

• Borderline tool-vs-learning-material call, resolved as a tool: these are machine-facing agent skills/plugins you install (/plugin install ...), not human docs, consistent with the catalog's existing AI/MCP entries.
• Adjusted from the submission: title skills-for-fabric -> Skills for Fabric; trimmed tags to conventions; omitted language (repo is Markdown/JSON skill definitions, no primary programming language).

Closes #23