fix: strip BOM character from templates

.changeset/twelve-mayflies-decide.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: strip BOM character from templates

packages/svelte/src/compiler/utils/sanitize_template_string.js

@@ -1,7 +1,12 @@
+const BOM_CHARACTER = String.fromCharCode(65279);
+
 /**
  * @param {string} str
  * @returns {string}
  */
 export function sanitize_template_string(str) {
-	return str.replace(/(`|\${|\\)/g, '\\$1');
+	return str
+		.replace(/(`|\${|\\)/g, '\\$1')
+		.replaceAll(BOM_CHARACTER, '')
+		.replaceAll('', '');
 }

packages/svelte/tests/runtime-legacy/samples/whitespace-bom/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: '<div></div>'
+});

packages/svelte/tests/runtime-legacy/samples/whitespace-bom/main.svelte

@@ -0,0 +1,2 @@
+
+<div>&#xFEFF;</div>