feat: add StreamedResponse for streaming response bodies

Adds a `StreamedResponse` class extending `Response`, enabling chunked
transfer encoding for streaming response bodies via readable streams.

Automatically sets `transfer-encoding: chunked` if not specified.

Closes #9

Author: zefir-git

src/response/StreamedResponse.ts

@@ -0,0 +1,28 @@
+import http from "node:http";
+import stream from "node:stream/promises";
+import {Request} from "../Request.js";
+import {Response} from "./Response.js";
+
+/**
+ * A response that streams data from a readable stream.
+ */
+export class StreamedResponse<A> extends Response<A> {
+    private readonly stream: NodeJS.ReadableStream;
+
+    /**
+     * Construct a StreamedResponse.
+     * @param stream The readable stream to send in the response body.
+     * @param [statusCode=200] The HTTP response status code to send.
+     * @param [headers] The HTTP response headers to send.
+     */
+    public constructor(stream: NodeJS.ReadableStream, statusCode = 200, headers?: HeadersInit) {
+        super(statusCode, headers);
+        this.stream = stream;
+        if (!this.headers.has("transfer-encoding")) this.headers.set("transfer-encoding", "chunked");
+    }
+
+    protected override async send(res: http.ServerResponse, req?: Request<A>): Promise<void> {
+        this.writeHead(res, req);
+        await stream.pipeline(this.stream, res);
+    }
+}