* feat(llms): add llms txt output format
- Introduced a new output format 'llms' in the configuration.
- Updated the example site to utilize the new 'llms' format for the home output.
- Added a new layout file 'llms.txt' for rendering content in the LLMS format.
* docs: add llms.txt support documentation
- Introduced a new section in the configuration guide detailing how to enable the llms.txt output format for improved accessibility to large language models.
- Provided example configuration for adding the 'llms' output format in the site's hugo.yaml.
- Explained the content structure of the generated llms.txt file, including site title, section listings, page summaries, and direct links.
* Update configuration.md
