Add issue-triage Claude skill for GitHub issue management

[m3nu]

Add a Claude Code skill that provides guidelines for triaging and classifying GitHub issues. The policy covers:

• Bug prioritization by severity
• Feature request evaluation criteria
• When to use status:idea vs status:wontfix
• Comment templates for common scenarios
• Label combination quick reference

Also update .gitignore to allow .claude/skills/ to be committed while keeping other .claude/ contents ignored.

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read the CONTRIBUTING guide.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

I provide my contribution under the terms of the license of this repository and I affirm the Developer Certificate of Origin.