style: simplify rel matching

docs: public API work

feat: create new Link from parsing string slice

perf: parse Uris from string slices

fix: add proper error handling to Rel parsing

feat: add TryFrom<&str> for Rel

style: simplify rel module with macros

docs: improve public API

feat: add registered relation types

docs: add README

test: add very simple deserializing test

feat: add ResourceDescriptor type

feat: add Link type

feat: add Uri type

chore: initial commit