dev-test: JSDOM's Event and CustomEvent win over Node's in the browser env

Globals were only set where Node had none, and Node defines Event and
CustomEvent itself. Code running in the browser env therefore built
Node events, which a JSDOM node refuses: react-tooltip's
window.dispatchEvent(new CustomEvent(...)) threw "parameter 1 is not of
type 'Event'". In the browser env these two now come from JSDOM, as they
do under jest-environment-jsdom.

packages/dev-test/src/env/browser.spec.ts

@@ -23,4 +23,9 @@ describe('browser', () => {
   it('contains HTML*Element', () => {
     expect(typeof all.HTMLElement).toBe('function');
   });
+
+  it('dispatches the global CustomEvent and Event on window', () => {
+    expect(() => window.dispatchEvent(new CustomEvent('custom', { detail: 1 }))).not.toThrow();
+    expect(() => window.dispatchEvent(new Event('plain'))).not.toThrow();
+  });
 });