First add of PowerShell instructions

[whiteken]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• My contribution adds a new instruction, prompt, or chat mode file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, or chat mode with GitHub Copilot.
• I have run node update-readme.js and verified that README.md is up to date.

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Description

This PR introduces a new file: instructions/powershell.instructions.md, providing guidance for effective use of GitHub Copilot with PowerShell. The PowerShell instructions file is structured to align with Microsoft's cmdlet development guidelines and the existing format of this repository. It includes:

• Naming conventions (verb-noun, PascalCase, parameter and variable naming)
• Cmdlet parameter design (including [switch], validation, -PassThru, and ValueFromPipeline)
• Proper use of the pipeline, output practices, and structured object emission
• Idiomatic error handling using ShouldProcess, Write-* streams, try/catch, and non-interactive design
• Style guidance including formatting, alias avoidance, comment-based help, and automation-friendly structure
• Several code examples and a full end-to-end cmdlet implementation pattern

Changes

• Added: instructions/powershell.instructions.md
• Updated: readme.md

References

• Based on: PowerShell Strongly Encouraged Development Guidelines (Microsoft Docs)

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Type of Contribution

• New instruction file.
• New prompt file.
• New chat mode file.
• Other (please specify):

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.

[Copilot]

Pull Request Overview

This PR adds a new PowerShell instructions file and updates the README to include it.

• Introduces instructions/powershell.instructions.md with cmdlet development guidelines.
• Updates README.md to list the PowerShell instructions.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
instructions/powershell.instructions.md	New PowerShell cmdlet and scripting best practices document
README.md	Added PowerShell entry to the instructions index

[Copilot]

Front matter values should use single quotes instead of double quotes. Change applyTo to use single quotes.