Add encoder benchmark

Author: szuend

bench/encode.bench.ts

@@ -0,0 +1,31 @@
+// Copyright 2025 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import { expandGlob } from "jsr:@std/fs";
+import { format } from "jsr:@std/fmt/bytes";
+
+import { decode, encode } from "../mod.ts";
+
+const BENCHMARKS = await (async () => {
+  const result = [];
+  for await (
+    const file of expandGlob("*.js.map", { root: import.meta.dirname })
+  ) {
+    const mapContent = Deno.readTextFileSync(file.path);
+    const mapJson = JSON.parse(mapContent);
+    const info = decode(mapJson);
+    result.push({
+      name: file.name,
+      info,
+      size: mapContent.length,
+    });
+  }
+  return result;
+})();
+
+for (const { name, info, size } of BENCHMARKS) {
+  Deno.bench(`${name}, ${format(size)}`, () => {
+    encode(info);
+  });
+}