Add test that ROSLIB is accessible globally from importing the UMD bu…

…ndle

test/cdn-import.test.js

@@ -0,0 +1,8 @@
+import { describe, it, expect } from 'vitest';
+import '../dist/RosLib.umd.cjs';
+
+describe('Using as if imported from a CDN', () => {
+  it('Adds itself to the global namespace', () => {
+    expect(globalThis.ROSLIB).toBeTruthy();
+  })
+});