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/editorconfig/lib/cli.d.ts

@@ -0,0 +1,14 @@
+import { type OutputConfiguration } from 'commander';
+import * as editorconfig from './';
+/**
+ * Command line interface for editorconfig.  Pulled out into a separate module
+ * to make it easier to test.
+ *
+ * @param args Usually process.argv.  Note that the first two parameters are
+ * usually 'node' and 'editorconfig'
+ * @param testing If testing, you may pass in a Commander OutputConfiguration
+ * so that you can capture stdout and stderror.  If `testing` is provided,
+ * this routine will throw an error instead of calling `process.exit`.
+ * @returns An array of combined properties, one for each file argument.
+ */
+export default function cli(args: string[], testing?: OutputConfiguration): Promise<editorconfig.Props[]>;