Not support Erlang/OTP 20+

[HJianBo]

Env: Erlang/OTP 20+

Exec following code

> {ok, Salt} = bcrypt:gen_salt().

exception error:

** exception exit: {{function_clause,[{bcrypt_nif_worker,terminate,
                                                         [{undef,[{crypto,rand_bytes,[16],[]},
                                                                  {bcrypt_nif,gen_salt,1,
                                                                              [{file,"src/bcrypt_nif.erl"},{line,57}]},
                                                                  ...

[peffis]

Is anyone already working on upgrading bcrypt to OTP 20 and above? I would like to upgrade my application to OTP 20+ but a dependency to bcrypt forces me to erlang 19 unfortunately. I can possibly look into it myself if nobody is working on it already.