Integrate giscuss into the website

App is installed, we just need to do it

See [the docs](https://squidfunk.github.io/mkdocs-material/setup/adding-a-comment-system/)

The issue references integrating giscuss into the website, likely for a comment system. Start by examining the project's documentation setup, possibly using mkdocs-material as indicated. Review the linked mkdocs-material documentation to understand the configuration steps. Check for existing configuration files (like mkdocs.yml) to see where the comment system needs to be added.

索引モデルが issue の本文から書いたものです。