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/core-js-pure/modules/esnext.reflect.get-own-metadata.js

@@ -0,0 +1,17 @@
+'use strict';
+// TODO: Remove from `core-js@4`
+var $ = require('../internals/export');
+var ReflectMetadataModule = require('../internals/reflect-metadata');
+var anObject = require('../internals/an-object');
+
+var ordinaryGetOwnMetadata = ReflectMetadataModule.get;
+var toMetadataKey = ReflectMetadataModule.toKey;
+
+// `Reflect.getOwnMetadata` method
+// https://github.com/rbuckton/reflect-metadata
+$({ target: 'Reflect', stat: true }, {
+  getOwnMetadata: function getOwnMetadata(metadataKey, target /* , targetKey */) {
+    var targetKey = arguments.length < 3 ? undefined : toMetadataKey(arguments[2]);
+    return ordinaryGetOwnMetadata(metadataKey, anObject(target), targetKey);
+  }
+});