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/https-proxy-agent/dist/agent.d.ts

@@ -0,0 +1,30 @@
+/// <reference types="node" />
+import net from 'net';
+import { Agent, ClientRequest, RequestOptions } from 'agent-base';
+import { HttpsProxyAgentOptions } from '.';
+/**
+ * The `HttpsProxyAgent` implements an HTTP Agent subclass that connects to
+ * the specified "HTTP(s) proxy server" in order to proxy HTTPS requests.
+ *
+ * Outgoing HTTP requests are first tunneled through the proxy server using the
+ * `CONNECT` HTTP request method to establish a connection to the proxy server,
+ * and then the proxy server connects to the destination target and issues the
+ * HTTP request from the proxy server.
+ *
+ * `https:` requests have their socket connection upgraded to TLS once
+ * the connection to the proxy server has been established.
+ *
+ * @api public
+ */
+export default class HttpsProxyAgent extends Agent {
+    private secureProxy;
+    private proxy;
+    constructor(_opts: string | HttpsProxyAgentOptions);
+    /**
+     * Called when the node-core HTTP client library is creating a
+     * new HTTP request.
+     *
+     * @api protected
+     */
+    callback(req: ClientRequest, opts: RequestOptions): Promise<net.Socket>;
+}