feat(popper): arrow option & docs consistency across components (#875)

docs/components/content/examples/ContextMenuExampleOffset.vue

@@ -0,0 +1,35 @@
+<script setup>
+const { x, y } = useMouse()
+const { y: windowY } = useWindowScroll()
+
+const isOpen = ref(false)
+const virtualElement = ref({ getBoundingClientRect: () => ({}) })
+
+function onContextMenu () {
+  const top = unref(y) - unref(windowY)
+  const left = unref(x)
+
+  virtualElement.value.getBoundingClientRect = () => ({
+    width: 0,
+    height: 0,
+    top,
+    left
+  })
+
+  isOpen.value = true
+}
+</script>
+
+<template>
+  <div class="w-full" @contextmenu.prevent="onContextMenu">
+    <Placeholder class="h-96 select-none w-full flex items-center justify-center">
+      Right click here
+    </Placeholder>
+
+    <UContextMenu v-model="isOpen" :virtual-element="virtualElement" :popper="{ offset: 0 }">
+      <div class="p-4">
+        Menu
+      </div>
+    </UContextMenu>
+  </div>
+</template>