Fix t:Data.Parser.KV.field_spec/2 and t:Data.Parser.KV.field/2

[zachallaun]

In t:field_spec/2, the type variables a and b correspond to Parser.t(a, b), where a is the success type and b is the failure type. The type definition calls field_opts(b), defined as:

@type field_opts(a) :: [{:optional, bool()} | {:default, a} | {:from, field_name()}]

This would suggest that the :default would be the failure type b, while it should actually be a default corresponding to the success type a.

The opaque t:field/2 had the same issue.

---

• Fix t:Data.Parser.KV.field_spec/2 and t:Data.Parser.KV.field/2
• Update deps and improve generated documentation by adding links to source (it will assume release tags of the form "MAJOR.MINOR.PATCH", which is the format used in this repo already)

Note that the "0.6.0" tag seems to be missing in this repo at the moment.