Extra line after a type and before a comment prevents edoc from parsing it correctly

[elbrujohalcon]

Describe the bug
The default formatter adds an empty line after an attribute if it finds a comment below it. That's an issue because EDoc uses comments after -types to document those types and it does not work if there is an empty line between one thing and the other.
For a more detailed explanation, check @erszcz's amazing comment here: inaka/worker_pool#200 (comment)

To Reproduce
Try to format a module containing this:

-opaque another_list(X) :: [X].
%% another_list() is a kind of list...

The formatter turns it into…

-opaque another_list(X) :: [X].

%% another_list() is a kind of list...

Expected behavior
The text should remain as is.