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/flex-shrink.js

@@ -0,0 +1,39 @@
+let Declaration = require('../declaration')
+let flexSpec = require('./flex-spec')
+
+class FlexShrink extends Declaration {
+  /**
+   * Return property name by final spec
+   */
+  normalize() {
+    return 'flex-shrink'
+  }
+
+  /**
+   * Return flex property for 2012 spec
+   */
+  prefixed(prop, prefix) {
+    let spec
+    ;[spec, prefix] = flexSpec(prefix)
+    if (spec === 2012) {
+      return prefix + 'flex-negative'
+    }
+    return super.prefixed(prop, prefix)
+  }
+
+  /**
+   * Ignore 2009 spec and use flex property for 2012
+   */
+  set(decl, prefix) {
+    let spec
+    ;[spec, prefix] = flexSpec(prefix)
+    if (spec === 2012 || spec === 'final') {
+      return super.set(decl, prefix)
+    }
+    return undefined
+  }
+}
+
+FlexShrink.names = ['flex-shrink', 'flex-negative']
+
+module.exports = FlexShrink