Feat Request: Allow more control over response type

When fetching data from static image, it might be nice to give users more control over the response type. For example:

import mbClient from "@mapbox/mapbox-sdk";
import StaticImage from "@mapbox/mapbox-sdk/services/static";

const client = mbClient({accessToken: "..."});
const staticImageService = StaticImage(client);

staticImageService.getStaticImage({ ... })
  .send({ responseType: 'blob' })
  .then(res => {
    // do something with res
  });

I poked around the code and didn't find any way to override the response type. I'm happy to send a PR for this. LMK 👍

Start by locating the static image service's getStaticImage entry point and the request handling behind send(). Trace how response types are currently selected, then check the surrounding service behavior before making a change. Done means callers can pass responseType, including 'blob', and receive the requested response type.