Add WeChat MP Downloader skill

[KKK25843]

Summary

Add KKK25843/wechat-mp-downloader-skill to the Domain-Specific Skills section with the required GitHub stars badge.

Why it belongs

• it is a Codex-native SKILL.md workflow rather than a general-purpose AI tool
• it covers a distinct archive use case: 1-20 WeChat Official Accounts over a shared date range
• it saves Markdown with local images and supports title preview, keyword filters, and resumable state
• authentication remains in the user's browser; it does not export cookies or automate CAPTCHA
• the public v0.1.0 release includes offline CI for macOS, Windows, and Linux on Python 3.10 and 3.13

Validation

• checked the list for an existing duplicate
• git diff --check
• used the required flat-square star badge format