Add support for Link header pagination

[smaeda-ks]

client example:

	paginator := client.NewListACLEntriesPaginator(
		&fastly.ListACLEntriesInput{
			ServiceID: serviceID,
			ACLID:     "your_acl_id",
			PerPage:   50,
		},
	)

	var es []*fastly.ACLEntry
	for paginator.HasNext() {
		data, err := paginator.GetNext()
		if err != nil {
			break
		}
		es = append(es, data...)
	}

Adding NewListACLEntriesPaginator and NewListDictionaryItemsPaginator.

[smaeda-ks]

@Integralist let me know if you have any questions.

[Integralist]

LGTM but have a couple of suggestions.

Out of interest, do you happen to know how to get the generated documentation to display an example snippet like in your PR description (not sure if that's done by adding the snippet into a code comment above the code function)?

[smaeda-ks]

@Integralist Thanks. Applied all suggestions and added code examples. Tested this locally using godoc. This should work.
ref. https://go.dev/blog/examples