repair regexp routes

test/apps/basics/src/routes/[id([0-9]+)].svelte

@@ -0,0 +1,8 @@
+<script>
+	import { stores } from '@sapper/app';
+	const { page } = stores();
+</script>
+
+<h1>Regexp page {$page.params.id}</h1>
+
+<a href="regexp/234">nested regexp route</a>

test/apps/basics/src/routes/[slug].svelte

@@ -3,4 +3,6 @@
 	const { page } = stores();
 </script>
 
-<h1>{$page.params.slug.toUpperCase()}</h1>
+<h1>{$page.params.slug}</h1>
+
+<a href="234">regexp route</a>

test/apps/basics/src/routes/regexp/[id([0-9]+)].svelte

@@ -0,0 +1,6 @@
+<script>
+	import { stores } from '@sapper/app';
+	const { page } = stores();
+</script>
+
+<h1>Nested regexp page {$page.params.id}</h1>