fix: treeshake internal storage.get helper (#13998)

Author: Rich-Harris

.changeset/heavy-ants-reply.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: treeshake internal `storage.get` helper

packages/kit/src/runtime/client/session-storage.js

@@ -3,6 +3,7 @@
  * @param {string} key
  * @param {(value: string) => any} parse
  */
+/*@__NO_SIDE_EFFECTS__*/
 export function get(key, parse = JSON.parse) {
 	try {
 		return parse(sessionStorage[key]);