Styles function heads so that they're as small as possible.

The goal is that a function head fits on a single line.

This isn't a Credo issue, and the formatter is fine with either approach. But Quokka has opinions!

Ex:

This long declaration

def foo(%{
  bar: baz
}) do
  ...
endcopy

Becomes

def foo(%{bar: baz}) do
  ...
endcopy