📖 [Docs]: Add GitHub Actions and PowerShell coding standards

[Marius Storhaug (MariusStorhaug)]

Adds comprehensive standards documentation for coding practices and GitHub Actions workflows.

Included

GitHub Actions Standards (NEW)

• \src/docs/GitHub-Actions/Standards.md\ - Comprehensive workflow authoring and review standards
  • Job naming conventions
  • Step naming conventions
  • Shell choice guidelines
  • Permissions and access control
  • Reusable workflow patterns
  • Concurrency and cancellation
  • Caching best practices
  • Matrix strategy usage
  • Environment variables and secrets
• \src/docs/GitHub-Actions/index.md\ - GitHub Actions documentation hub

PowerShell Coding Standards (Expanded)

Individual standard documents for better navigation and focused reference:

• \Code-Layout.md\ - Brace style, indentation, spacing
• \Control-Flow.md\ - if/else, try/catch, loops
• \Documentation.md\ - Comment types, examples, help blocks
• \Function-Structure.md\ - Parameter blocks, output patterns
• \Naming.md\ - Function, variable, and module naming conventions
• \Output-and-Errors.md\ - Write-Output patterns, error handling
• \Performance.md\ - Optimization patterns and techniques
• \Readability.md\ - Best practices for readable code
• \Security.md\ - Credential handling, input validation
• \Testing.md\ - Pester testing practices
• \index.md\ - Standards overview

Why

These standards provide critical guidance for:

• GitHub Actions workflow authoring and review across the organization
• PowerShell coding practices and conventions
• Consistent code style and patterns
• Better developer experience and knowledge sharing

Extracted from PSModule/docs PR #61 to serve as organization-wide standards in MSXOrg/docs.

[Marius Storhaug (MariusStorhaug)]

Closed in favor of #53. The original PR added parallel standards trees, but #53 folds only the genuinely missing guidance into the existing canonical Coding-Standards pages.