OTP 27 docs

[whatyouhide]

Yo! You folks interested in moving the docs to -doc docs from OTP 27? Simplifies the syntax quite a bit thanks to Markdown. I started working on this but figured I'd ask first 🙃

[wojtekmach]

@whatyouhide sorry if stating the obvious, I was looking into doing same for hex_core and the following approach with ?MODULEDOC and ?DOC macros seems promising:

-module(foo).
-export([foo/0]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC("""
The foo module.
""").

?DOC("""
The foo module.
""").
foo() ->
  ok.

[whatyouhide]

@wojtekmach that's not obvious at all! Yeah I thought this was not needed as -doc attrs would just be ignored, but the issue is """ strings which are not supported <27. Great catch!

[whatyouhide]

Closing in favor of #134.