AI metadata generator

It would be useful to have a metadata generator using LLMs.

This feature should introduce one package (maybe llm-utils), set its only dependency to be utils and use it for LLM helpers used in netlogo-docs.

The generator should have this interface or a similar one:

generateShortDescription(content: string, metadata: /* stringifyable */, instructions: string = ""): Promise<string>

generateLongDescription(content: string, metadata: /* stringifyable */, instructions: string = ""): Promise<string>

generateSEOKeywords(content: string, metadata: /* stringifyable */, instructions: string = ""): Promise<Array<string>>