Split the code, add file server example.

src/Content.ts

@@ -0,0 +1,22 @@
+import { Range } from "./parseRangeHeader";
+import { Stream } from "stream";
+export type Content = {
+  /**
+   * Returns a readable stream based on the provided range (optional).
+   * @param {Range} range The start-end range of stream data.
+   * @returns {Stream} A readable stream
+   */
+  getStream(range?: Range): Stream;
+  /**
+   * Total size of the content
+   */
+  readonly totalSize: number;
+  /**
+   * Mime type to be sent in Content-Type header
+   */
+  readonly mimeType: string;
+  /**
+   * File name to be sent in Content-Disposition header
+   */
+  readonly fileName: string;
+};