Revise accessibility instructions for clarity and detail

[weboverhauls]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• I have read and followed the Guidance for submissions involving paid services.
• My contribution adds a new instruction, prompt, agent, skill, or workflow 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, agent, skill, or workflow with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.
• I am targeting the staged branch for this pull request.

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Description

• Add a reference.
• Clarify "alt" text.
• Add Multimedia section.
• Add Other section.

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Type of Contribution

• New instruction file.
• New prompt file.
• New agent file.
• New plugin.
• New skill file.
• New agentic workflow.
• Update to existing instruction, prompt, agent, plugin, skill, or workflow.
• Other (please specify):

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Additional Notes

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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

Updates the existing Markdown accessibility instruction set to be clearer and more comprehensive for reviewers of .md content, adding additional references and expanding coverage beyond links/images/headings.

Changes:

• Added an additional external reference (Smashing Magazine) alongside the existing GitHub guidance.
• Clarified image guidance by renaming the section to “Image Alternative (alt) Text”.
• Introduced new sections for Multimedia and other miscellaneous accessibility considerations, and updated the review priority list accordingly.

Show a summary per file

File	Description
instructions/markdown-accessibility.instructions.md	Expands and clarifies Markdown accessibility review guidance, adding new sections and a new reference.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 2