Updated button width in documentation/reactivity

Fixed button width in order to avoid the changing width of the button in the result when the text changes from 'time' to 'times'

documentation/tutorial/02-reactivity/01-reactive-assignments/app-a/App.svelte

@@ -5,7 +5,11 @@
 		// event handler code goes here
 	}
 </script>
-
+<style>
+button{
+width:200px;
+}
+</style>
 <button>
 	Clicked {count}
 	{count === 1 ? 'time' : 'times'}