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/postcss-flexbugs-fixes/bugs/bug81a.js

@@ -0,0 +1,27 @@
+var postcss = require('postcss');
+
+module.exports = function(decl) {
+  var regex = /(\d{1,}) (\d{1,}) (calc\(.*\))/g;
+  var matches = regex.exec(decl.value);
+  if (decl.prop === 'flex' && matches) {
+    var grow = postcss.decl({
+      prop: 'flex-grow',
+      value: matches[1],
+      source: decl.source
+    });
+    var shrink = postcss.decl({
+      prop: 'flex-shrink',
+      value: matches[2],
+      source: decl.source
+    });
+    var basis = postcss.decl({
+      prop: 'flex-basis',
+      value: matches[3],
+      source: decl.source
+    });
+    decl.parent.insertBefore(decl, grow);
+    decl.parent.insertBefore(decl, shrink);
+    decl.parent.insertBefore(decl, basis);
+    decl.remove();
+  }
+};