feat: add ErrInvalidResolveTarget

refactor: ResolveTo now can take mult-level pointers

If we have T in the resolver. Now ResolveTo() can take *T, **T, ***T
values. It used to only consider *T as valid.

chore(ci): upgrade codecov to v4 and add TOKEN

feat: expose Resolver.Copy

Merge pull request #9 from shiar/main

endless loop following self referential structs

feat: allow sorting directives WithDirectiveRunOrder

fix: define nested and non-nested directives

fix: can override option in Resolve/Scan, rename WithNestedDirectives…

…Enabled

chore: fix GitHub action, upgrade Go 1.19 -> 1.20

feat: allow overriding namespace when calling Scan and Resolve

also...

1. removed the ReplaceDirectiveExecutor API
2. removed some error constants