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/csso/lib/replace/property/font-weight.js

@@ -0,0 +1,22 @@
+module.exports = function compressFontWeight(node) {
+    var value = node.children.head.data;
+
+    if (value.type === 'Identifier') {
+        switch (value.name) {
+            case 'normal':
+                node.children.head.data = {
+                    type: 'Number',
+                    loc: value.loc,
+                    value: '400'
+                };
+                break;
+            case 'bold':
+                node.children.head.data = {
+                    type: 'Number',
+                    loc: value.loc,
+                    value: '700'
+                };
+                break;
+        }
+    }
+};