Implement composite action wrapping issues-helper functionality

[Copilot]

Creates a GitHub Actions skill that provides unified interface to all 26 actions from actions-cool/issues-helper@v3.

Implementation

• action.yml: Composite action with 40+ inputs and 10+ outputs mapping to issues-helper parameters
• README.md: Usage examples for common scenarios (welcome issues, label management, inactive checks, batch operations)
• .github/workflows/example.yml: Reference implementations with explicit permissions

Usage

- uses: actions-cool/issues-helper-skill@v1
  with:
    actions: 'create-comment,add-labels'
    body: 'Thank you @${{ github.event.issue.user.login }}'
    labels: 'needs-triage'
    emoji: '+1,heart'

Supports all base actions (add-assignees, create-comment, update-issue, etc.) and advanced actions (check-inactive, find-issues, mark-duplicate, etc.).

Original prompt

这是一个 skill，可以快速使用 issues-helper 的全部功能。

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