New To Cabal - First cabal library

file to edit: https://github.com/haskell/cabal-userguide/blob/main/src/new_to_cabal/06_first_cabal_library.md

## Brief Summary

This chapter should walk the user through getting a library set up via their cabal repo. Ideally it will build on the previous chapter that walks the user through top level `.cabal` file properties. It should also explain how to make modules visible, and how to load the library into ghci or cabal repl to test things out.

## Prior Art

[Haskell School library and executable](https://schooloffp.co/2020/08/17/whirlwind-tour-of-cabal-for-beginners.html#having-a-project-with-both-library-and-executable)
[Haskell School module visibility](https://schooloffp.co/2020/08/17/whirlwind-tour-of-cabal-for-beginners.html#configuring-visibility-of-modules-in-a-library)

# Resources

[Old cabal user guide library vs executable](https://cabal.readthedocs.io/en/3.4/developing-packages.html#editing-the-cabal-file)