message: fix: Make it also work if someone passes request obj
diff: @@ -4,6 +4,7 @@ import { Event, EventProcessor, Integration, Severity, Span, SpanContext, Transa
  import {
  addInstrumentationHandler,
  getGlobalObject,
  + isInstanceOf,
  isMatchingPattern,
  logger,
  safeJoin,
  @@ -1019,18 +1020,24 @@ function fetchCallback(handlerData: { [key: string]: any }): void {
  if (activity) {
  const span = activity.span;
  if (span) {
  + const request = (handlerData.args[0] = handlerData.args[0] as string | Request);
  const options = (handlerData.args[1] = (handlerData.args[1] as { [key: string]: any }) || {});
  - if (options.headers) {
  - if (typeof options.headers.append === 'function') {
  - options.headers.append('sentry-trace', span.toTraceparent());
  - } else if (Array.isArray(options.headers)) {
  - options.headers = [...options.headers, ['sentry-trace', span.toTraceparent()]];
  + let headers = options.headers;
  + if (isInstanceOf(request, Request)) {
  + headers = (request as Request).headers;
  + }
  + if (headers) {
  + if (typeof headers.append === 'function') {
  + headers.append('sentry-trace', span.toTraceparent());
  + } else if (Array.isArray(headers)) {
  + headers = [...headers, ['sentry-trace', span.toTraceparent()]];
  } else {
  - options.headers = { ...options.headers, 'sentry-trace': span.toTraceparent() };
  + headers = { ...headers, 'sentry-trace': span.toTraceparent() };
  }
  } else {
  - options.headers = { 'sentry-trace': span.toTraceparent() };
  + headers = { 'sentry-trace': span.toTraceparent() };
  }
  + options.headers = headers;
  }
  }
  }
  