fourmolu (Haskell formatter)

[ssoelvsten]

Having all code formatted by mechanically has multiple benefits:

• Consistent styling, which decreases cognitive load (more brainpower to solve problems rather than parsing the code).
• Ease refactoring efforts, e.g. when renaming a variable one does not have to go through indenting everything anew by hand.

This also includes a new GitHub action which will complain if code in a pull requests (or pushed directly to a branch) is not properly formatted.

[ssoelvsten]

I've marked this pull request as a draft since merging it would be a headache to other, e.g. #53 , #68 , and more. The merge of this needs to be coordinated.