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/fastq/example.js

@@ -0,0 +1,14 @@
+'use strict'
+
+/* eslint-disable no-var */
+
+var queue = require('./')(worker, 1)
+
+queue.push(42, function (err, result) {
+  if (err) { throw err }
+  console.log('the result is', result)
+})
+
+function worker (arg, cb) {
+  cb(null, 42 * 2)
+}