web/polyfills: add polyfill for AbortSignal.timeout

web/src/lib/polyfills/abortsignal-timeout.ts

@@ -0,0 +1,10 @@
+import { browser } from "$app/environment";
+
+if (browser && 'AbortSignal' in window && !window.AbortSignal.timeout) {
+    window.AbortSignal.timeout = (milliseconds: number) => {
+        const controller = new AbortController();
+        setTimeout(() => controller.abort("timed out"), milliseconds);
+
+        return controller.signal;
+    }
+}