site: adds example to goto documentation (#1055)

Author: kevmodrome

site/content/docs/03-client-api.md

@@ -31,7 +31,20 @@ sapper.start({
 
 Programmatically navigates to the given `href`. If the destination is a Sapper route, Sapper will handle the navigation, otherwise the page will be reloaded with the new `href`. In other words, the behaviour is as though the user clicked on a link with this `href`.
 
-Returns a `Promise` that resolves when the navigation is complete.
+Returns a `Promise` that resolves when the navigation is complete. This can be used to perform actions once the navigation has completed, such as updating a database, store, etc.
+
+```js
+import { goto } from '@sapper/app';
+
+const navigateAndSave = async () => {
+	await goto('/');
+	saveItem();
+}
+
+const saveItem = () => {
+	// do something with the database
+}
+```
 
 
 ### prefetch(href)