Added navigator mock before tests to allow tests in headless mode

[kkerti]

Use this before the tests:

test.beforeEach(({ page }) => {
  // mocks navigator.serial, so headless UI tests can run!
  page.addInitScript(
    "Object.defineProperty(navigator,'serial',{set: () => undefined, get: () => undefined})"
  );
});

[github-actions]

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