feat: add fenced-code-meta rule

[TKDev7]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

This pull request introduces a new rule, fenced-code-meta, that enforces a consistent policy for metadata in fenced code block info strings. It allows teams to require metadata when a language is specified or to disallow metadata entirely.

What changes did you make? (Give an overview)

• Added a rule that validates the presence or absence of metadata based on the configured mode
• Added documentation
• Added tests

Related Issues

Fixes #477

Is there anything you'd like reviewers to focus on?

[Copilot]

Pull Request Overview

This pull request introduces a new ESLint rule fenced-code-meta that enforces consistent policies for metadata in fenced code block info strings. The rule can either require metadata when a language is specified ("always" mode) or disallow metadata entirely ("never" mode).

• Added a new rule that validates the presence or absence of metadata in fenced code blocks
• Comprehensive test coverage for both backtick and tilde fenced code blocks with various configurations
• Complete documentation with examples and usage guidelines

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/rules/fenced-code-meta.js	Implements the core rule logic for validating fenced code block metadata
tests/rules/fenced-code-meta.test.js	Comprehensive test suite covering valid and invalid cases for both rule modes
docs/rules/fenced-code-meta.md	User documentation with examples and configuration options
README.md	Updates rule table and formatting improvements for ESLint disable comments

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[nzakas]

Thanks for working on this. Overall it looks good. I think the Copilot comments bring up good points, so please take a look at those. Also, double-check the CI errors.

[nzakas]

LGTM. Would like another review before merging.

[nzakas]

@TKDev7 when you're available again, please take a look at the comments here.