Update slots.md (#2806)

* Update slots.md

Update documentation in order to indicate how to use conditional render of default slot

* Update slots.md

Fix typo

* Update slots.md

* Update src/guide/components/slots.md

---------

Co-authored-by: Natalia Tepluhina <[email protected]>

Author: claushellsing

src/guide/components/slots.md

@@ -302,8 +302,8 @@ Sometimes you want to render something based on whether or not a slot is present
 
 You can use the [$slots](/api/component-instance.html#slots) property in combination with a [v-if](/guide/essentials/conditional.html#v-if) to achieve this.
 
-In the example below we define a Card component with two conditional slots: `header` and `footer`.
-When the header / footer is present we want to wrap them to provide additional styling:
+In the example below we define a Card component with three conditional slots: `header`, `footer` and the `default` one.
+When the header / footer / default is present we want to wrap them to provide additional styling:
 
 ```vue-html
 <template>
@@ -312,7 +312,7 @@ When the header / footer is present we want to wrap them to provide additional s
       <slot name="header" />
     </div>
     
-    <div class="card-content">
+    <div v-if="$slots.default" class="card-content">
       <slot />
     </div>
     
@@ -323,7 +323,7 @@ When the header / footer is present we want to wrap them to provide additional s
 </template>
 ```
 
-[Try it in the Playground](https://play.vuejs.org/#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)
+[Try it in the Playground](https://play.vuejs.org/#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)
 
 ## Dynamic Slot Names {#dynamic-slot-names}