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/@pmmmwh/react-refresh-webpack-plugin/loader/utils/getIdentitySourceMap.js

@@ -0,0 +1,30 @@
+const { SourceMapGenerator } = require('source-map');
+
+/**
+ * Generates an identity source map from a source file.
+ * @param {string} source The content of the source file.
+ * @param {string} resourcePath The name of the source file.
+ * @returns {import('source-map').RawSourceMap} The identity source map.
+ */
+function getIdentitySourceMap(source, resourcePath) {
+  const sourceMap = new SourceMapGenerator();
+  sourceMap.setSourceContent(resourcePath, source);
+
+  source.split('\n').forEach((line, index) => {
+    sourceMap.addMapping({
+      source: resourcePath,
+      original: {
+        line: index + 1,
+        column: 0,
+      },
+      generated: {
+        line: index + 1,
+        column: 0,
+      },
+    });
+  });
+
+  return sourceMap.toJSON();
+}
+
+module.exports = getIdentitySourceMap;