docs: add Agent Skills Hub to Resources directory

[zhuyansen]

Summary

Adds Agent Skills Hub to the Resources section as a third-party directory of MCP servers + Claude Skills + agent tools.

Why this fits

The Resources section already lists peer directories (MCPHub, MCPServers.com, Smithery, mcp.run, PulseMCP, OpenTools, etc.). Agent Skills Hub serves a complementary slice:

• Indexes 67,000+ open-source projects from GitHub (vs. the curated awesome-* lists)
• Quality-scored on 10 dimensions (completeness / clarity / specificity / examples / readme structure / agent readiness, plus 4 community signals) — methodology open-source at github.com/zhuyansen/agent-skills-hub
• Refreshed every 8 hours via GitHub Actions sync
• Free + open source (CC BY-NC-SA on data, MIT on code)

Compliance check

• Read CONTRIBUTING.md — community resources/directories are permitted in this section
• Alphabetical placement (between A2A-MCP Java Bridge and AiMCP)
• Format matches existing entries (bold link + " - " separator + descriptor + maintainer link)
• Not a "new server implementation" (per CONTRIBUTING, those go to MCP Registry)

Happy to adjust formatting / wording per maintainer preference.

[zhuyansen]

Two notes for the maintainer to save time on review:

1. The failing check-readme-only CI is a known upstream bot permission issue, not a content problem.

The bot tries POST /repos/.../issues/4060/labels to add readme: pending but gets 403 Resource not accessible by integration because GitHub Actions on fork PRs don't have issues: write by default. This is exactly what #3840 (still open) is trying to fix — see the same error pattern reported in #4022 by @Will-hxw.

The bot's underlying detection logic correctly identified this PR as README-only; it just couldn't write the label.

2. This PR adds to the 📚 Resources section, not the retired Third-Party Servers section (#3950).

I checked recent README PRs (#3964, #4022, #3590, #3511) all got closed with a template reply that "third-party server list has been retired in favor of MCP Registry" — happy to confirm that doesn't apply here:

• This is not a server submission — AgentSkillsHub is a directory/aggregator, peer to MCPHub, MCPServers.com, Smithery, mcp.run, PulseMCP, OpenTools, Open-Sourced MCP Servers Directory, etc., all of which currently live in the Resources section
• The Resources section was untouched by Retire third-party server list in favor of MCP Registry #3950 (which only removed ## Official Integrations and ## Community Servers)
• Inserted alphabetically between A2A-MCP Java Bridge and AiMCP, format matches existing entries

Happy to adjust per any maintainer preference. Thanks for considering.