Fix duplicate elements (sveltejs/sapper#1725)

Author: babeard

src/client.js

@@ -1,5 +1,7 @@
 import * as sapper from '@sapper/app';
 
-sapper.start({
-	target: document.querySelector('#sapper')
+window.addEventListener('load', () => {
+	sapper.start({
+		target: document.querySelector('#sapper')
+	});
 });

src/template.html

@@ -10,10 +10,9 @@
 	<link rel="stylesheet" href="global.css">
 	<link rel="manifest" href="manifest.json" crossorigin="use-credentials">
 	<link rel="icon" type="image/png" href="favicon.png">
-
 	<!-- Sapper creates a <script> tag containing `src/client.js`
-	     and anything else it needs to hydrate the app and
-	     initialise the router -->
+		and anything else it needs to hydrate the app and
+		initialise the router -->
 	%sapper.scripts%
 
 	<!-- Sapper generates a <style> tag containing critical CSS
@@ -29,5 +28,7 @@
 	<!-- The application will be rendered inside this element,
 	     because `src/client.js` references it -->
 	<div id="sapper">%sapper.html%</div>
+
+
 </body>
 </html>