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/yargs/build/lib/typings/common-types.js

@@ -0,0 +1,9 @@
+export function assertNotStrictEqual(actual, expected, shim, message) {
+    shim.assert.notStrictEqual(actual, expected, message);
+}
+export function assertSingleKey(actual, shim) {
+    shim.assert.strictEqual(typeof actual, 'string');
+}
+export function objectKeys(object) {
+    return Object.keys(object);
+}

node_modules/yargs/build/lib/typings/yargs-parser-types.js

@@ -0,0 +1 @@
+export {};