Handle raw bytes in http request bodies

[BSchneppe]

Something like this gets serialized to the string 1,2,3

const arr = new Uint8Array(3)
arr[0] = 1;
arr[1] = 2;
arr[2] = 3;
const req: HttpRequest = {
    url: "https://httpbin.io/post",
    method: "POST",
  };
Http.request(req,arr)

We should give more control to the user, allowing to send raw bytes (even non-utf8) if so desired