Pick up latest md language server

[mjbvz]

Fixes #310682

[Copilot]

Pull request overview

Updates the built-in Markdown extension’s dependency graph to pick up a newer vscode-markdown-languageservice release, ensuring the extension no longer relies on a transitive dependency for its TypeScript type import.

Changes:

• Add vscode-markdown-languageservice@^0.5.0-alpha.13 as a direct devDependency.
• Update the extension’s lockfile to resolve vscode-markdown-languageservice to 0.5.0-alpha.13 (including its node >=18 engine metadata).

Show a summary per file

File	Description
extensions/markdown-language-features/package.json	Adds vscode-markdown-languageservice as a direct dev dependency so type imports don’t rely on transitive deps.
extensions/markdown-language-features/package-lock.json	Updates the resolved vscode-markdown-languageservice package to 0.5.0-alpha.13 and records its engine requirement.

Copilot's findings

Files not reviewed (1)

• extensions/markdown-language-features/package-lock.json: Language not supported

• Files reviewed: 1/2 changed files
• Comments generated: 0