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/escape-string-regexp/index.js

@@ -0,0 +1,13 @@
+'use strict';
+
+module.exports = string => {
+	if (typeof string !== 'string') {
+		throw new TypeError('Expected a string');
+	}
+
+	// Escape characters with special meaning either inside or outside character sets.
+	// Use a simple backslash escape when it’s always valid, and a \unnnn escape when the simpler form would be disallowed by Unicode patterns’ stricter grammar.
+	return string
+		.replace(/[|\\{}()[\]^$+*?.]/g, '\\$&')
+		.replace(/-/g, '\\x2d');
+};