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/bug6.js

@@ -0,0 +1,16 @@
+var postcss = require('postcss');
+
+module.exports = function(decl) {
+  if (decl.prop === 'flex') {
+    var values = postcss.list.space(decl.value);
+    var flexGrow = values[0];
+    var flexShrink = values[1] || '1';
+    var flexBasis = values[2] || '0%';
+    // Safari seems to hate '0%' and the others seems to make do with a nice value when basis is missing,
+    // so if we see a '0%', just remove it.  This way it'll get adjusted for any other cases where '0%' is
+    // already defined somewhere else.
+    if (flexBasis === '0%') flexBasis = null;
+    decl.value =
+      flexGrow + ' ' + flexShrink + (flexBasis ? ' ' + flexBasis : '');
+  }
+};