Draft: Update files at /docs

Description

Polishing documentation

Related issue

https://gitlab.com/postgres-ai/docs/-/issues/137

Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
• this MR contains API changes and they have been reviewed OR there are no API changes