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/autoprefixer/lib/hacks/overscroll-behavior.js

@@ -0,0 +1,33 @@
+let Declaration = require('../declaration')
+
+class OverscrollBehavior extends Declaration {
+  /**
+   * Return property name by spec
+   */
+  normalize() {
+    return 'overscroll-behavior'
+  }
+
+  /**
+   * Change property name for IE
+   */
+  prefixed(prop, prefix) {
+    return prefix + 'scroll-chaining'
+  }
+
+  /**
+   * Change value for IE
+   */
+  set(decl, prefix) {
+    if (decl.value === 'auto') {
+      decl.value = 'chained'
+    } else if (decl.value === 'none' || decl.value === 'contain') {
+      decl.value = 'none'
+    }
+    return super.set(decl, prefix)
+  }
+}
+
+OverscrollBehavior.names = ['overscroll-behavior', 'scroll-chaining']
+
+module.exports = OverscrollBehavior