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/clean-css/lib/optimizer/level-1/property-optimizers/box-shadow.js

@@ -0,0 +1,15 @@
+var plugin = {
+  level1: {
+    property: function boxShadow(_rule, property) {
+      var values = property.value;
+
+      // remove multiple zeros
+      if (values.length == 4 && values[0][1] === '0' && values[1][1] === '0' && values[2][1] === '0' && values[3][1] === '0') {
+        property.value.splice(2);
+        property.dirty = true;
+      }
+    }
+  }
+};
+
+module.exports = plugin;