docs: add query param to hide the demo preview

demos/preview/Demo.vue

@@ -17,6 +17,7 @@
     <div class="overflow-hidden">
       <div
         class="bg-white"
+        :class="[hidePreview ? 'hidden' : '']"
       >
         <demo-frame
           :src="currentIframeUrl"
@@ -140,6 +141,10 @@ export default {
       return this.query.hideSource || false
     },
 
+    hidePreview() {
+      return this.query.hidePreview || false
+    },
+
     githubUrl() {
       return `https://github.com/ueberdosis/tiptap/tree/main/demos/src/${this.name}`
     },