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-arguments/test/index.js

@@ -0,0 +1,47 @@
+'use strict';
+
+var test = require('tape');
+// eslint-disable-next-line no-extra-parens
+var isArguments = /** @type {import('..') & { isLegacyArguments: import('..') }} */ (require('../'));
+var hasToStringTag = require('has-tostringtag/shams')();
+
+test('primitives', function (t) {
+	t.notOk(isArguments([]), 'array is not arguments');
+	t.notOk(isArguments({}), 'object is not arguments');
+	t.notOk(isArguments(''), 'empty string is not arguments');
+	t.notOk(isArguments('foo'), 'string is not arguments');
+	t.notOk(isArguments({ length: 2 }), 'naive array-like is not arguments');
+	t.end();
+});
+
+test('arguments object', function (t) {
+	t.ok(isArguments(arguments), 'arguments is arguments');
+	t.notOk(isArguments(Array.prototype.slice.call(arguments)), 'sliced arguments is not arguments');
+	t.end();
+});
+
+test('old-style arguments object', function (t) {
+	var isLegacyArguments = isArguments.isLegacyArguments || isArguments;
+	var fakeOldArguments = {
+		callee: function () {},
+		length: 3
+	};
+	t.ok(isLegacyArguments(fakeOldArguments), 'old-style arguments is arguments');
+	t.end();
+});
+
+test('Symbol.toStringTag', { skip: !hasToStringTag }, function (t) {
+	/** @type {{ [Symbol.toStringTag]?: string }} */
+	var obj = {};
+	obj[Symbol.toStringTag] = 'Arguments';
+	t.notOk(isArguments(obj), 'object with faked toStringTag is not arguments');
+
+	/** @type {IArguments & { [Symbol.toStringTag]?: string }} */
+	var args = (function () {
+		return arguments;
+	}());
+	args[Symbol.toStringTag] = 'Arguments';
+	t.notOk(isArguments(obj), 'real arguments with faked toStringTag is not arguments');
+
+	t.end();
+});