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/messages/plugin-conflict.js

@@ -0,0 +1,22 @@
+"use strict";
+
+module.exports = function(it) {
+    const { pluginId, plugins } = it;
+
+    let result = `ESLint couldn't determine the plugin "${pluginId}" uniquely.
+`;
+
+    for (const { filePath, importerName } of plugins) {
+        result += `
+- ${filePath} (loaded in "${importerName}")`;
+    }
+
+    result += `
+
+Please remove the "plugins" setting from either config or remove either plugin installation.
+
+If you still can't figure out the problem, please stop by https://eslint.org/chat/help to chat with the team.
+`;
+
+    return result;
+};