Support go versions pre go1.23

[lordvidex]

The use of iterators prevents versions pre go1.23 not to compile. Build constraints can be used to write some working implementation for iterators for older go versions

[lordvidex]

Actually, this is more complicated. PR in #5 shows that program can at least build for go1.22. For go1.23, error is returned because the go.mod has version <go1.23. Changing it to go1.23 will also force other libraries importing errs to update to go1.23.

[lordvidex]

In order to resolve breaking changes. A new major version errs/v2 has been released. New features and updates pushed to main will now be released as part of v2. However, <go1.23 versions of errs will continue to be actively maintained on the v1 branch.