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/indent-string/index.js

@@ -0,0 +1,35 @@
+'use strict';
+
+module.exports = (string, count = 1, options) => {
+	options = {
+		indent: ' ',
+		includeEmptyLines: false,
+		...options
+	};
+
+	if (typeof string !== 'string') {
+		throw new TypeError(
+			`Expected \`input\` to be a \`string\`, got \`${typeof string}\``
+		);
+	}
+
+	if (typeof count !== 'number') {
+		throw new TypeError(
+			`Expected \`count\` to be a \`number\`, got \`${typeof count}\``
+		);
+	}
+
+	if (typeof options.indent !== 'string') {
+		throw new TypeError(
+			`Expected \`options.indent\` to be a \`string\`, got \`${typeof options.indent}\``
+		);
+	}
+
+	if (count === 0) {
+		return string;
+	}
+
+	const regex = options.includeEmptyLines ? /^/gm : /^(?!\s*$)/gm;
+
+	return string.replace(regex, options.indent.repeat(count));
+};