chore: allow preview site to work offline in local dev (#11091)

Author: Rich-Harris

sites/svelte-5-preview/src/lib/workers/bundler/index.js

@@ -260,6 +260,9 @@ async function get_bundle(uid, mode, cache, local_files_lookup) {
 		name: 'svelte-repl',
 		async resolveId(importee, importer) {
 			if (uid !== current_id) throw ABORT;
+
+			if (importee === 'esm-env') return importee;
+
 			const v5 = is_v5();
 			const v4 = !v5 && is_v4();
 
@@ -358,6 +361,10 @@ async function get_bundle(uid, mode, cache, local_files_lookup) {
 		async load(resolved) {
 			if (uid !== current_id) throw ABORT;
 
+			if (resolved === 'esm-env') {
+				return `export const BROWSER = true; export const DEV = true`;
+			}
+
 			const cached_file = local_files_lookup.get(resolved);
 			if (cached_file) return cached_file.source;