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/readme.md

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+# escape-string-regexp [![Build Status](https://travis-ci.org/sindresorhus/escape-string-regexp.svg?branch=master)](https://travis-ci.org/sindresorhus/escape-string-regexp)
+
+> Escape RegExp special characters
+
+## Install
+
+```
+$ npm install escape-string-regexp
+```
+
+## Usage
+
+```js
+const escapeStringRegexp = require('escape-string-regexp');
+
+const escapedString = escapeStringRegexp('How much $ for a 🦄?');
+//=> 'How much \\$ for a 🦄\\?'
+
+new RegExp(escapedString);
+```
+
+You can also use this to escape a string that is inserted into the middle of a regex, for example, into a character class.
+
+---
+
+<div align="center">
+	<b>
+		<a href="https://tidelift.com/subscription/pkg/npm-escape-string-regexp?utm_source=npm-escape-string-regexp&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
+	</b>
+	<br>
+	<sub>
+		Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
+	</sub>
+</div>