Add issue templates, disable blank issues, and configure Dependabot

[Copilot]

Adds structured issue templates with icons for bug reports and feature requests, disables blank issues, and configures automated dependency management.

Issue Templates

Bug Report (.github/ISSUE_TEMPLATE/bug_report.yml)

• Structured form with icons: 🐛 bug description, 📋 reproduction steps, ✅ expected, ❌ actual behavior
• Dropdowns for OS (Windows/Linux/macOS/FreeBSD) and .NET version (8.0/9.0/10.0)
• Required fields enforce complete bug reports

Feature Request (.github/ISSUE_TEMPLATE/feature_request.yml)

• Icons for: 💡 proposed solution, 🎯 problem statement, 🔄 alternatives, 🤝 contribution intent
• Structured fields guide clear feature proposals

Config (.github/ISSUE_TEMPLATE/config.yml)

• blank_issues_enabled: false
• Redirects general questions to GitHub Discussions

Dependabot

Configuration (.github/dependabot.yml)

• Weekly updates for NuGet packages and GitHub Actions
• Auto-labels PRs: dependencies, nuget, github-actions
• Commit prefix: chore

Original prompt

I would like to extend this repository with:

• An issue template for bug reporting (with icons)
• An issue template for feature requests (with icons)

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.