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/@csstools/postcss-progressive-custom-properties/CHANGELOG.md

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+# Changes to PostCSS Progressive Custom Properties
+
+## 1.3.0 (March 7, 2022)
+
+- Add matching rules for `color-mix`
+- Fix matching rules for gradient functions
+- Reduce matchers size
+
+## 1.2.0 (February 15, 2022)
+
+- More matching rules for [double position gradients](https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-double-position-gradients#readme).
+
+## 1.1.0 (February 12, 2022)
+
+- No longer uses custom properties in `@supports` rules.
+- Implement AST matching for values and units and generate minimal `@supports` for select features.
+
+## 1.0.0 (February 6, 2022)
+
+Initial release