Index.Exists doesn't accept options (and so context)

- Algolia Client Version: 3.26.1

### Description

Currently the function [index.Exists](https://github.com/algolia/algoliasearch-client-go/blob/15d0de75e06af571cff6db73e340f000bf5d278f/algolia/search/index.go#L107) doesn't accept options like other functions.

We use `opts` to pass the current context. With a custom `Requester` (`http.client`) it's allow us to do tracing.
Without opts we can trace correctly this `Exists` function 😞

Is it possible to add `opts` on `Exists` function, like this ?
```go
func (i *Index) Exists(opts ...interface{}) (bool, error) {
_, err := i.GetSettings(opts)
if err == nil {
return true, nil
}
if _, ok := errs.IsAlgoliaErrWithCode(err, http.StatusNotFound); ok {
return false, nil
}
return false, err
}
```

I can create a PR to fix this 👍🏻

Start in algolia/search/index.go at Index.Exists and compare its signature with other functions that accept options. Check how Exists delegates to GetSettings and how opts reach the custom Requester; done means Exists accepts and forwards options while preserving its existing true, false, and error behavior.

Written by the indexing model from the issue text.