Update getting started to install layerchart@next

Author: techniq

packages/layerchart/src/routes/getting-started/+page.svelte

@@ -73,7 +73,7 @@
   <h2>Install package</h2>
 
   <div>Install <code>layerchart</code> package</div>
-  <Code source={`npm install layerchart`} language="sh" />
+  <Code source={`npm install layerchart@next`} language="sh" />
 
   <Blockquote>
     <div>