New To Cabal - First cabal executable

file to edit: https://github.com/haskell/cabal-userguide/blob/main/src/new_to_cabal/07_first_cabal_executable.md

## Brief Summary

This chapter should build off of the previous one https://github.com/haskell/cabal-userguide/issues/14 and demonstrate how to create an executable that uses the library. However, it would be a good idea to show that an executable can exist without depending on the library. It might be nice to show 2 executables that use the same library, this would demonstrate that there can be more than one `exe` unlike libraries. It would also be nice to show the user how to run their executable.

## Prior Art

[Kowainik blog adding an executable](https://kowainik.github.io/posts/2018-06-21-haskell-build-tools#cabal-adding-executable)
[Haskell School building and running executables](https://schooloffp.co/2020/08/17/whirlwind-tour-of-cabal-for-beginners.html#building-and-running-executables)

## Resources

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