ci: add AI issue reviewer

[bartlomieju]

Adding an AI reviewer using https://github.com/marketplace/actions/ai-assessment-comment-labeler.

[Copilot]

Pull Request Overview

This PR introduces an automated AI-powered issue triage system for external contributors. The workflow uses AI to analyze and provide initial assessments of newly opened issues, helping to streamline the triage process for the Deno project.

Key changes:

• Adds a GitHub Actions workflow that triggers on new issues from non-organization members
• Implements three AI prompt templates for different issue types (bugs, features, questions)
• Configures the workflow to use GPT-4o-mini with a 500 token limit for assessments

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/issue_ai_review.yml	Main workflow definition that triggers AI assessment on new issues from external contributors
.github/prompts/bug-assessment.prompt.yml	AI prompt template for analyzing and triaging bug reports
.github/prompts/feature-assessment.prompt.yml	AI prompt template for analyzing and triaging feature requests
.github/prompts/question-assessment.prompt.yml	AI prompt template for analyzing and triaging user questions

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[Copilot]

The condition excludes MEMBER and OWNER but doesn't account for COLLABORATOR, who typically also has write access to the repository. Consider adding '&& github.event.issue.author_association != 'COLLABORATOR'' to the condition to exclude all trusted contributors from AI review.

Suggested change

	if: github.event.issue.author_association != 'MEMBER' && github.event.issue.author_association != 'OWNER'
	if: github.event.issue.author_association != 'MEMBER' && github.event.issue.author_association != 'OWNER' && github.event.issue.author_association != 'COLLABORATOR'

[bartlomieju]

Closing in favor of #31211 for now