Added a very complicated AsyncIterableReader class.

The class was already implemented in
"https://deno.land/std@0.144.0/streams/conversion.ts".  So, I litterally
lost 1 day of work!  I hate myself.

vendor/deno.land/std@0.188.0/streams/copy.ts

@@ -0,0 +1,48 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+// This module is browser compatible.
+
+import { DEFAULT_BUFFER_SIZE } from "./_common.ts";
+import type { Reader, Writer } from "../types.d.ts";
+
+/** Copies from `src` to `dst` until either EOF (`null`) is read from `src` or
+ * an error occurs. It resolves to the number of bytes copied or rejects with
+ * the first error encountered while copying.
+ *
+ * ```ts
+ * import { copy } from "https://deno.land/std@$STD_VERSION/streams/copy.ts";
+ *
+ * const source = await Deno.open("my_file.txt");
+ * const bytesCopied1 = await copy(source, Deno.stdout);
+ * const destination = await Deno.create("my_file_2.txt");
+ * const bytesCopied2 = await copy(source, destination);
+ * ```
+ *
+ * @param src The source to copy from
+ * @param dst The destination to copy to
+ * @param options Can be used to tune size of the buffer. Default size is 32kB
+ */
+export async function copy(
+  src: Reader,
+  dst: Writer,
+  options?: {
+    bufSize?: number;
+  },
+): Promise<number> {
+  let n = 0;
+  const bufSize = options?.bufSize ?? DEFAULT_BUFFER_SIZE;
+  const b = new Uint8Array(bufSize);
+  let gotEOF = false;
+  while (gotEOF === false) {
+    const result = await src.read(b);
+    if (result === null) {
+      gotEOF = true;
+    } else {
+      let nwritten = 0;
+      while (nwritten < result) {
+        nwritten += await dst.write(b.subarray(nwritten, result));
+      }
+      n += nwritten;
+    }
+  }
+  return n;
+}