Feature request: preserve more blank lines in function body

[iwinux]

With option sequence-blank-line = preserve-one (added by #814), blank lines in sequences are preserved as expected, but other blank lines in function body are still "eaten".

For example (code adapted from Cohttp example):

let async_main =
  let* resp, raw_body = Client.get (Uri.of_string "https://api.github.com/") in

  let* body = Body.to_string raw_body in
  let code = resp |> Response.status |> Code.code_of_status in

  Printf.printf "Status: %d\n" code;
  Printf.printf "Body: %s\n" body;
  Lwt.return ()

becomes

let async_main =
  let* resp, raw_body = Client.get (Uri.of_string "https://api.github.com/") in
  let* body = Body.to_string raw_body in
  let code = resp |> Response.status |> Code.code_of_status in
  Printf.printf "Status: %d\n" code;
  Printf.printf "Body: %s\n" body;
  Lwt.return ()

It would be great if such blank lines are left intact, so that some blocks of logic can "stand out" by keeping "distance" from other blocks.