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/css-loader/dist/runtime/getUrl.js

@@ -0,0 +1,26 @@
+"use strict";
+
+module.exports = function (url, options) {
+  if (!options) {
+    options = {};
+  }
+  if (!url) {
+    return url;
+  }
+  url = String(url.__esModule ? url.default : url);
+
+  // If url is already wrapped in quotes, remove them
+  if (/^['"].*['"]$/.test(url)) {
+    url = url.slice(1, -1);
+  }
+  if (options.hash) {
+    url += options.hash;
+  }
+
+  // Should url be wrapped?
+  // See https://drafts.csswg.org/css-values-3/#urls
+  if (/["'() \t\n]|(%20)/.test(url) || options.needQuotes) {
+    return "\"".concat(url.replace(/"/g, '\\"').replace(/\n/g, "\\n"), "\"");
+  }
+  return url;
+};