Docs - Add a short summary blurb to each major doc section

[theangchen]

1. Add a short summary blurb to each major doc section.
2. Ensure that each card's preview text is something that describes the section rather than just being the first few words from the section itself

Example: https://nmfs-radfish.github.io/documentation/docs/category/libraries

Right below “Libraries” something like: “These are the two libraries used within the RADFish framework for building applications. radfish is used to handle utilities like state management while react-radfish serves as the react bindings for our utilities.