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/overlay/containers/RuntimeErrorContainer.js

@@ -0,0 +1,29 @@
+const PageHeader = require('../components/PageHeader.js');
+const RuntimeErrorStack = require('../components/RuntimeErrorStack.js');
+const Spacer = require('../components/Spacer.js');
+
+/**
+ * @typedef {Object} RuntimeErrorContainerProps
+ * @property {Error} currentError
+ */
+
+/**
+ * A container to render runtime error messages with stack trace.
+ * @param {Document} document
+ * @param {HTMLElement} root
+ * @param {RuntimeErrorContainerProps} props
+ * @returns {void}
+ */
+function RuntimeErrorContainer(document, root, props) {
+  PageHeader(document, root, {
+    message: props.currentError.message,
+    title: props.currentError.name,
+    topOffset: '2.5rem',
+  });
+  RuntimeErrorStack(document, root, {
+    error: props.currentError,
+  });
+  Spacer(document, root, { space: '1rem' });
+}
+
+module.exports = RuntimeErrorContainer;