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/is-negative-zero/test/index.js

@@ -0,0 +1,29 @@
+'use strict';
+
+var test = require('tape');
+var isNegativeZero = require('../');
+
+test('not negative zero', function (t) {
+	// @ts-expect-error
+	t.notOk(isNegativeZero(), 'undefined is not negative zero');
+	t.notOk(isNegativeZero(null), 'null is not negative zero');
+	t.notOk(isNegativeZero(false), 'false is not negative zero');
+	t.notOk(isNegativeZero(true), 'true is not negative zero');
+	t.notOk(isNegativeZero(0), 'positive zero is not negative zero');
+	t.notOk(isNegativeZero(Infinity), 'Infinity is not negative zero');
+	t.notOk(isNegativeZero(-Infinity), '-Infinity is not negative zero');
+	t.notOk(isNegativeZero(NaN), 'NaN is not negative zero');
+	t.notOk(isNegativeZero('foo'), 'string is not negative zero');
+	t.notOk(isNegativeZero([]), 'array is not negative zero');
+	t.notOk(isNegativeZero({}), 'object is not negative zero');
+	t.notOk(isNegativeZero(function () {}), 'function is not negative zero');
+	t.notOk(isNegativeZero(-1), '-1 is not negative zero');
+
+	t.end();
+});
+
+test('negative zero', function (t) {
+	t.ok(isNegativeZero(-0), 'negative zero is negative zero');
+	t.end();
+});
+