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/error-stack-clear.js

@@ -0,0 +1,16 @@
+'use strict';
+var uncurryThis = require('../internals/function-uncurry-this');
+
+var $Error = Error;
+var replace = uncurryThis(''.replace);
+
+var TEST = (function (arg) { return String(new $Error(arg).stack); })('zxcasd');
+// eslint-disable-next-line redos/no-vulnerable, sonarjs/slow-regex -- safe
+var V8_OR_CHAKRA_STACK_ENTRY = /\n\s*at [^:]*:[^\n]*/;
+var IS_V8_OR_CHAKRA_STACK = V8_OR_CHAKRA_STACK_ENTRY.test(TEST);
+
+module.exports = function (stack, dropEntries) {
+  if (IS_V8_OR_CHAKRA_STACK && typeof stack == 'string' && !$Error.prepareStackTrace) {
+    while (dropEntries--) stack = replace(stack, V8_OR_CHAKRA_STACK_ENTRY, '');
+  } return stack;
+};