Enables sandbox on about window

ts/context/config.ts

@@ -0,0 +1,12 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { RendererConfigType } from '../types/RendererConfig';
+import { strictAssert } from '../util/assert';
+
+const params = new URLSearchParams(document.location.search);
+const configParam = params.get('config');
+strictAssert(typeof configParam === 'string', 'config is not a string');
+const config: RendererConfigType = JSON.parse(configParam);
+
+export { config };