Add copilot instructions

[nkolev92]

Basically the nuget docs version of https://github.com/dotnet/docs/blame/main/.github/copilot-instructions.md.

This should allow us to use copilot to write GH docs, or at least do the first version of them.

[Copilot]

Pull Request Overview

This PR adds GitHub Copilot instructions to help AI-assisted documentation writing for the .NET NuGet docs repository. The instructions establish writing guidelines, style conventions, and formatting standards to ensure consistent, high-quality documentation output.

• Establishes comprehensive writing style guide aligned with Microsoft standards
• Defines formatting conventions and file naming rules for consistency
• Includes AI disclosure requirements and workflow guidance

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

This guideline contradicts standard Markdown practices and accessibility recommendations. Sequential numbering (1., 2., 3.) provides better structure for screen readers and is the conventional approach. Consider revising this requirement or providing justification for the deviation.

Suggested change

	- Number all ordered list items as "1." (not sequential numbering like "1.", "2.", "3.", etc.)
	- Use sequential numbering for ordered list items ("1.", "2.", "3.", etc.) to follow standard Markdown practices and accessibility recommendations.

[Copilot]

This instruction assumes Copilot can interact with GitHub workflows and build systems autonomously, which may not be accurate. Consider clarifying that this is guidance for human reviewers working with AI-generated content, or revising to reflect actual AI capabilities.

Suggested change

	- When you (Copilot) are assigned an issue in GitHub, after you've completed your work and the workflows (status checks) have run, check to make sure there are no build warnings under the OpenPublishing.Build status check. If there are, open the build report (under View Details) and resolve any build warnings you introduced.
	- When you are assigned an issue in GitHub that involves Copilot-generated content, after completing your work and the workflows (status checks) have run, check to make sure there are no build warnings under the OpenPublishing.Build status check. If there are, open the build report (under View Details) and resolve any build warnings introduced by the changes.

[learn-build-service-prod]

Learn Build status updates of commit 20c8de9:

✅ Validation status: passed

File	Status	Preview URL	Details
.github/copilot-instructions.md	✅Succeeded

For more details, please refer to the build report.

[learn-build-service-prod]

PoliCheck Scan Report

The following report lists PoliCheck issues in PR files. Before you merge the PR, you must fix all severity-1 issues. Other issues are also a high priority. The AI Review Details column lists suggestions for either removing or replacing the terms. If you find a false positive result, mention it in a PR comment and include this text: #policheck-false-positive. This feedback helps reduce false positives in future scans.

✅ No issues found

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