Replace request with axios

[acalcutt]

This is a cherry pick of the PR acalcutt#284 submitted by @mjj203 in my old fork. I have updated it a little to fix some things changed in the current release.

This replaces request, which is unmaintained and has serveral vulnerabilies, with axios.

Fixes #1006

[mnutt]

This looks good to me. Great to see us replacing request.

axios is a good batteries-included http library. In my fork I used undici, which (as of node 16) will become the official node.js request library and uses web-standard fetch, but I think axios is also a good choice.

The code looks fine too. Down the road we might have an opportunity to refactor the maplibre data loading; maybe to something like:

const renderer = new mbgl.Map({
  mode: mode,
  ratio: ratio,
  request: (req, callback) => {
    requestMap(req.url)
      .then((data) => callback(null, data))
      .catch((err) => callback(err, null));
});

function requestMap(url) {
  const protocol = url.split(":")[0];

  if (protocol === "sprites") {
    return requestSprites(url);
  } else if (protocol === "fonts") {
    return requestFonts(url);
  } else if (protocol === "mbtiles") {
    return requestMbtiles(url, dataDecoratorFunc);
  } else if (protocol === "http" || protocol === "https") {
    return requestUrl(url);
  } else {
    return Promise.reject(new Error(`Unkown protocol: ${protocol}`));
  }
}

This way we have the callback->promise transition fairly early on and can just deal in promises.