Suppress accessibility warnings from build log

(cherry picked from commit c18cba5bd90d1b685e224886fdd062e5043c2621)

Author: pedroborges

packages/svelte/test-app/svelte.config.js

@@ -1,6 +1,12 @@
 import { vitePreprocess } from '@sveltejs/vite-plugin-svelte'
 
 const config = {
+  onwarn(warning, onwarn) {
+    if (/A11y/.test(warning.message)) return
+
+    onwarn(warning)
+  },
+
   // Consult https://kit.svelte.dev/docs/integrations#preprocessors
   // for more information about preprocessors
   preprocess: vitePreprocess(),