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/es-abstract/2020/IsPromise.js

@@ -0,0 +1,24 @@
+'use strict';
+
+var callBound = require('call-bound');
+
+var $PromiseThen = callBound('Promise.prototype.then', true);
+
+var isObject = require('es-object-atoms/isObject');
+
+// https://262.ecma-international.org/6.0/#sec-ispromise
+
+module.exports = function IsPromise(x) {
+	if (!isObject(x)) {
+		return false;
+	}
+	if (!$PromiseThen) { // Promises are not supported
+		return false;
+	}
+	try {
+		$PromiseThen(x); // throws if not a promise
+	} catch (e) {
+		return false;
+	}
+	return true;
+};