Include more modern example of handling pagination

Consider the inclusion of something like the following in the package's README, as an alternative to the existing recommended boilerplate for handling paginated responses.

Generics were introduced in version `1.18`, and the `iter.Seq` function in `1.23`. Many existing and potential users of godo would benefit from an example utlising these packages:

```go
func Unpaginate[T any](ctx context.Context, f func(ctx context.Context, opt *godo.ListOptions) ([]T, *godo.Response, error), opt godo.ListOptions) iter.Seq2[T, error] {
return func(yield func(T, error) bool) {
var buffer T
for {
items, resp, err := f(ctx, &opt)
if err != nil {
yield(buffer, err)
return
}
for _, item := range items {
if !yield(item, nil) {
return
}
}
if resp.Links == nil || resp.Links.IsLastPage() {
return
}

page, err := resp.Links.CurrentPage()
if err != nil {
yield(buffer, err)
return
}

// set the page we want for the next request
opt.Page = page + 1
}
}
}
```

Start by finding the existing pagination boilerplate in the package README and compare it with the proposed Go generics and iter.Seq example. Done means the README includes a modern alternative for handling paginated responses, with the relevant Go version context and example presented clearly.

Written by the indexing model from the issue text.