feat(browser) add new v7 xhr transport

add makeNewXHRTransport function (WIP, needs testing(

Author: Lms24

packages/browser/src/transports/new-xhr.ts

@@ -0,0 +1,50 @@
+import {
+  BaseTransportOptions,
+  createTransport,
+  NewTransport,
+  TransportMakeRequestResponse,
+  TransportRequest,
+} from '@sentry/core';
+import { SyncPromise } from '@sentry/utils';
+
+export interface XHRTransportOptions extends BaseTransportOptions {
+  headers?: { [key: string]: string };
+}
+
+/**
+ * Creates a Transport that uses the XMLHttpRequest API to send events to Sentry.
+ */
+export function makeNewXHRTransport(options: XHRTransportOptions): NewTransport {
+  function makeRequest(request: TransportRequest): PromiseLike<TransportMakeRequestResponse> {
+    return new SyncPromise<TransportMakeRequestResponse>((resolve, _reject) => {
+      const xhr = new XMLHttpRequest();
+
+      xhr.onreadystatechange = (): void => {
+        if (xhr.readyState === 4) {
+          const headers = {
+            'x-sentry-rate-limits': xhr.getResponseHeader('X-Sentry-Rate-Limits'),
+            'retry-after': xhr.getResponseHeader('Retry-After'),
+          };
+          const response = {
+            body: xhr.response,
+            headers,
+            reason: xhr.statusText,
+            statusCode: xhr.status,
+          };
+
+          resolve(response);
+        }
+      };
+
+      xhr.open('POST', options.url);
+      for (const header in options.headers) {
+        if (Object.prototype.hasOwnProperty.call(options.headers, header)) {
+          xhr.setRequestHeader(header, options.headers[header]);
+        }
+      }
+      xhr.send(request.body);
+    });
+  }
+
+  return createTransport({ bufferSize: options.bufferSize }, makeRequest);
+}