Doc comments get placed on same line as external

[zploskey]

On the 3.1.0 version of refmt, a doc comment on the line preceding an external gets reformatted onto the same line as the external if it is short enough. I think we probably want to preserve the line break.

Before:

/** The url of the response. */
[@bs.send] external url : t => string = "";

After:

/** The url of the response. */ [@bs.send] external url : t => string = "";

[zploskey]

Also observed this:

/** The url of the response.                                      */ [@bs.send]
external url : t => string = "";