Skills: add missing dependency metadata (#1995)

Co-authored-by: jackheuberger <jackheuberger@users.noreply.github.com>

skills/github/SKILL.md

@@ -1,6 +1,7 @@
 ---
 name: github
 description: "Interact with GitHub using the `gh` CLI. Use `gh issue`, `gh pr`, `gh run`, and `gh api` for issues, PRs, CI runs, and advanced queries."
+metadata: {"clawdbot":{"emoji":"🐙","requires":{"bins":["gh"]},"install":[{"id":"brew","kind":"brew","formula":"gh","bins":["gh"],"label":"Install GitHub CLI (brew)"},{"id":"apt","kind":"apt","package":"gh","bins":["gh"],"label":"Install GitHub CLI (apt)"}]}}
 ---
 
 # GitHub Skill