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/is-docker/index.js

@@ -0,0 +1,29 @@
+'use strict';
+const fs = require('fs');
+
+let isDocker;
+
+function hasDockerEnv() {
+	try {
+		fs.statSync('/.dockerenv');
+		return true;
+	} catch (_) {
+		return false;
+	}
+}
+
+function hasDockerCGroup() {
+	try {
+		return fs.readFileSync('/proc/self/cgroup', 'utf8').includes('docker');
+	} catch (_) {
+		return false;
+	}
+}
+
+module.exports = () => {
+	if (isDocker === undefined) {
+		isDocker = hasDockerEnv() || hasDockerCGroup();
+	}
+
+	return isDocker;
+};