LLM support

This recipe makes sites AI-friendly by easing AI processing of site content and with that reducing processing costs. It provides complete coverage of the emerging llms.txt standard.

Included modules:
- /llms.txt - authoring and output of the /llms.txt file
- Markdownify - output each entity in MarkDown format
- Token Filter - token support for llms.txt authoring

Note: Output of all website content in a llms-full.txt file is not supported. Drupal site content is often so voluminous that serving it inside one text file would be prohibitive on multiple levels.