Make spellcheck available as an index processor

Hi! I'm interested in spellcheck/did-you-mean suggestions for decoupled search powered by Search API Decoupled as well, so I was glad to see your MR. I have it installed, but where should I expect to see that in my decoupled setup once I've added the processor? I don't see it as part of the endpoint when I try to set an obvious misspelling as the search query, which is where I was expecting to see it. Thanks!

This MR only makes the suggestions available on the Search API response which Search API Decoupled uses to build its response, exposing spellcheck still requires an alter event subscriber. Here's an example from Search Web Components https://git.drupalcode.org/project/search_web_components/-/blob/1.0.x/mo....