feat: add multi-module example showing moroutines from different modules on one worker

Co-Authored-By: Claude Opus 4.6 (1M context) <[e-mail]>

examples/multi-module/main.ts

···
+// Moroutines from different modules running on a single worker.
+// The worker lazily imports each module the first time a task from it is dispatched.
+// Requires Node v24+.
+//
+// Run: node examples/multi-module/main.ts
+
+import { workers } from '../../src/index.ts';
+import { square, add } from './math.ts';
+import { uppercase, repeat } from './text.ts';
+
+{
+  using run = workers(1);
+
+  // All four moroutines from two modules run on the same single worker
+  const results = await Promise.all([
+    run(square(7)),
+    run(add(3, 4)),
+    run(uppercase('hello')),
+    run(repeat('ab', 3)),
+  ]);
+
+  console.log('square(7)       =', results[0]); // 49
+  console.log('add(3, 4)       =', results[1]); // 7
+  console.log("uppercase('hello') =", results[2]); // HELLO
+  console.log("repeat('ab', 3) =", results[3]); // ababab
+}

examples/multi-module/math.ts

···
+import { mo } from '../../src/index.ts';
+
+export const square = mo(import.meta, (n: number): number => {
+  return n * n;
+});
+
+export const add = mo(import.meta, (a: number, b: number): number => {
+  return a + b;
+});

examples/multi-module/text.ts

···
+import { mo } from '../../src/index.ts';
+
+export const uppercase = mo(import.meta, (s: string): string => {
+  return s.toUpperCase();
+});
+
+export const repeat = mo(import.meta, (s: string, n: number): string => {
+  return s.repeat(n);
+});