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/internals/function-bind-context.js

@@ -0,0 +1,14 @@
+'use strict';
+var uncurryThis = require('../internals/function-uncurry-this-clause');
+var aCallable = require('../internals/a-callable');
+var NATIVE_BIND = require('../internals/function-bind-native');
+
+var bind = uncurryThis(uncurryThis.bind);
+
+// optional / simple context binding
+module.exports = function (fn, that) {
+  aCallable(fn);
+  return that === undefined ? fn : NATIVE_BIND ? bind(fn, that) : function (/* ...args */) {
+    return fn.apply(that, arguments);
+  };
+};