Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/workbox-broadcast-update/utils/constants.js

@@ -0,0 +1,16 @@
+/*
+  Copyright 2018 Google LLC
+
+  Use of this source code is governed by an MIT-style
+  license that can be found in the LICENSE file or at
+  https://opensource.org/licenses/MIT.
+*/
+import '../_version.js';
+export const CACHE_UPDATED_MESSAGE_TYPE = 'CACHE_UPDATED';
+export const CACHE_UPDATED_MESSAGE_META = 'workbox-broadcast-update';
+export const NOTIFY_ALL_CLIENTS = true;
+export const DEFAULT_HEADERS_TO_CHECK = [
+    'content-length',
+    'etag',
+    'last-modified',
+];