feat: ignore Go 1.20 errors.Join() sig by default (#37)

After upgrading to Go 1.20 and using the new `errors.Join()` from the
standard library, there is a false positive from `wrapcheck` saying that
error returned from external package is unwrapped, when `errors.Join()`
is now supposed to be an idiomatic way to wrap multiple errors from
external packages.

More info in the Go 1.20 release notes:

https://tip.golang.org/doc/go1.20#errors

Author: jacalvo

README.md

@@ -33,6 +33,7 @@ ignoreSigs:
 - .Errorf(
 - errors.New(
 - errors.Unwrap(
+- errors.Join(
 - .Wrap(
 - .Wrapf(
 - .WithMessage(

wrapcheck/wrapcheck.go

@@ -16,6 +16,7 @@ var DefaultIgnoreSigs = []string{
 	".Errorf(",
 	"errors.New(",
 	"errors.Unwrap(",
+	"errors.Join(",
 	".Wrap(",
 	".Wrapf(",
 	".WithMessage(",