docs(popover): add panel slot example

Resolves #763

docs/components/content/examples/PopoverExampleSlot.vue

@@ -0,0 +1,11 @@
+<template>
+  <UPopover>
+    <UButton color="white" label="Open" trailing-icon="i-heroicons-chevron-down-20-solid" />
+
+    <template #panel="{ close }">
+      <div class="p-8">
+        <UButton label="Close" @click="close" />
+      </div>
+    </template>
+  </UPopover>
+</template>

docs/content/6.overlays/3.popover.md

@@ -14,6 +14,7 @@ links:
 ::component-example
 #default
 :popover-example
+
 #code
 ```vue
 <template>
@@ -53,7 +54,27 @@ Use the `mode` prop to switch between `click` and `hover` modes.
 
 ### `panel`
 
-Use the `#panel` slot to fill the content of the panel.
+Use the `#panel` slot to fill the content of the panel. You will have access to the `open` property and the `close` method in the slot scope.
+
+::component-example
+#default
+:popover-example-slot
+
+#code
+```vue
+<template>
+  <UPopover>
+    <UButton color="white" label="Open" trailing-icon="i-heroicons-chevron-down-20-solid" />
+
+    <template #panel="{ close }">
+      <div class="p-8">
+        <UButton label="Close" @click="close" />
+      </div>
+    </template>
+  </UPopover>
+</template>
+```
+::
 
 ## Props