Add comprehensive guidelines for custom instruction files, localizati…

[SamErde]

…on, markdown standards, PowerShell Pester testing, and cmdlet development best practices

• Introduced a new instruction file for creating high-quality custom instruction files for GitHub Copilot.
• Added guidelines for localizing markdown documents, including directory structure and disclaimers.
• Established documentation and content creation standards for markdown files.
• Created a detailed guide for PowerShell Pester v5 testing best practices.
• Developed PowerShell cmdlet and scripting best practices based on Microsoft guidelines.
• Included guidelines for creating effective prompt files for GitHub Copilot.

[Copilot]

Pull Request Overview

This PR introduces comprehensive guidelines for custom instruction files, localization, markdown standards, PowerShell Pester testing, and cmdlet development best practices to guide GitHub Copilot in generating consistent, high-quality code across the repository.

Key Changes:

• Established standardized instruction file formats with required frontmatter and structured content
• Added PowerShell development standards covering cmdlet patterns, error handling, and pipeline support
• Created Pester v5 testing guidelines with setup/teardown patterns and assertion best practices

Reviewed Changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/instructions/prompt.instructions.md	Guidelines for creating effective prompt files with frontmatter requirements and workflow structure
.github/instructions/powershell.instructions.md	PowerShell cmdlet development standards including naming, parameters, pipeline support, and error handling
.github/instructions/powershell-pester-5.instructions.md	Pester v5 testing conventions covering test structure, mocking, data-driven tests, and best practices
.github/instructions/markdown.instructions.md	Documentation standards for markdown content including formatting rules and validation requirements
.github/instructions/localization.instructions.md	Guidelines for localizing markdown documents with directory structure and disclaimer requirements
.github/instructions/instructions.instructions.md	Meta-guidelines for creating high-quality custom instruction files for GitHub Copilot
.github/instructions/github-actions-ci-cd-best-practices.instructions.md	Comprehensive CI/CD pipeline guidance covering security, optimization, testing, and deployment strategies
.github/instructions/codacy.instructions.md	Configuration for AI behavior when interacting with Codacy's MCP Server
.github/instructions/a11y.instructions.md	Accessibility guidelines for creating WCAG 2.2 Level AA compliant code