support of jsonb in postgresql

[nosovk]

When I try to convert PGSQL ddl using sql2dbml I got errors on JSONB fields, for example:

create table profile.events
(
  id         uuid                     default gen_random_uuid() not null,
  data       jsonb                    default '{}'::jsonb       not null,
  created_at timestamp with time zone default now()             not null,
);

the part about ::jsonb broke conversion

[nguyenalter]

We don't currently support the PostgreSQL type cast :: operator. We'll let you know when we support this syntax.

[NQPhuc]

Fixed in #416