Enhanced plugin docs: Implement markdown parsing and CLI

[sunker]

What this PR does / why we need it:

This PR implements the core markdown parsing functionality for the plugin-docs-renderer package. It adds the ability to load documentation folders inc. manifest.json files, parse markdown content with YAML frontmatter and convert to HTML using GH flavored markdown. The package includes a CLI tool that processes a docs folder and dumps parsed JSON to stdout.

To test this:
This PR in the polystat panel has markdown docs + a manifest file with nested docs tree that can be used for testing.

npx @grafana/plugin-docs-renderer ./docs

Which issue(s) this PR fixes:

Fixes https://github.com/grafana/grafana-community-team/issues/737

Special notes for your reviewer:

The next couple of PRs will add template rendering, validation and a local dev server. Will add more unit tests then.

[github-actions]

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[Copilot]

Pull request overview

This PR implements core markdown parsing functionality for the @grafana/plugin-docs-renderer package. It introduces the ability to load documentation folders with manifest.json files, parse markdown content with YAML frontmatter, convert to HTML using GitHub Flavored Markdown, and provides a CLI tool for processing documentation folders.

Changes:

• Added markdown parser with frontmatter extraction using marked and gray-matter libraries
• Implemented documentation folder loader that recursively finds and reads markdown files
• Created CLI tool that processes docs folders and outputs parsed JSON to stdout
• Added comprehensive unit tests for the parser functionality

Reviewed changes

Copilot reviewed 5 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/plugin-docs-renderer/src/parser.ts	Implements markdown parsing with frontmatter extraction and GFM support
packages/plugin-docs-renderer/src/parser.test.ts	Comprehensive test coverage for parser functionality
packages/plugin-docs-renderer/src/loader.ts	Recursively loads markdown files and manifest from docs folder
packages/plugin-docs-renderer/src/index.ts	Updated exports to include new parser and loader functions
packages/plugin-docs-renderer/src/bin/run.ts	CLI tool that processes docs folders and outputs parsed JSON
packages/plugin-docs-renderer/package.json	Added dependencies (marked, gray-matter, minimist) and bin configuration
package-lock.json	Lock file updates for new dependencies

[academo]

left a nit for you to double check the type assertion on marked.parse but looking good!