fix: vue ssr (#867)

closes #840

Author: KABBOUCHI

packages/@headlessui-vue/src/hooks/use-window-event.ts

@@ -5,6 +5,8 @@ export function useWindowEvent<TType extends keyof WindowEventMap>(
   listener: (this: Window, ev: WindowEventMap[TType]) => any,
   options?: boolean | AddEventListenerOptions
 ) {
+  if (typeof window === 'undefined') return
+
   watchEffect(onInvalidate => {
     window.addEventListener(type, listener, options)