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/eslint-plugin-jsx-a11y/lib/util/getTabIndex.js

@@ -0,0 +1,33 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports["default"] = getTabIndex;
+var _jsxAstUtils = require("jsx-ast-utils");
+/**
+ * Returns the tabIndex value.
+ */
+function getTabIndex(tabIndex) {
+  var literalValue = (0, _jsxAstUtils.getLiteralPropValue)(tabIndex);
+
+  // String and number values.
+  if (['string', 'number'].indexOf(typeof literalValue) > -1) {
+    // Empty string will convert to zero, so check for it explicity.
+    if (typeof literalValue === 'string' && literalValue.length === 0) {
+      return undefined;
+    }
+    var value = Number(literalValue);
+    if (Number.isNaN(value)) {
+      return undefined;
+    }
+    return Number.isInteger(value) ? value : undefined;
+  }
+
+  // Booleans are not valid values, return undefined.
+  if (literalValue === true || literalValue === false) {
+    return undefined;
+  }
+  return (0, _jsxAstUtils.getPropValue)(tabIndex);
+}
+module.exports = exports.default;