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/lodash/_escapeHtmlChar.js

@@ -0,0 +1,21 @@
+var basePropertyOf = require('./_basePropertyOf');
+
+/** Used to map characters to HTML entities. */
+var htmlEscapes = {
+  '&': '&',
+  '<': '&lt;',
+  '>': '&gt;',
+  '"': '&quot;',
+  "'": '&#39;'
+};
+
+/**
+ * Used by `_.escape` to convert characters to HTML entities.
+ *
+ * @private
+ * @param {string} chr The matched character to escape.
+ * @returns {string} Returns the escaped character.
+ */
+var escapeHtmlChar = basePropertyOf(htmlEscapes);
+
+module.exports = escapeHtmlChar;