Expose properties of HttpProxyAgent (#29745)

* Expose properties of HttpProxyAgent

* Use 4 spaces over tabs

* Remove options & timeout properties

types/http-proxy-agent/http-proxy-agent-tests.ts

@@ -5,6 +5,9 @@ new Agent('url');
 new Agent({});
 new Agent({ host: 'url' });
 
+new Agent({}).proxy;
+new Agent({}).secureProxy;
+
 // $ExpectError
 new Agent();
 

types/http-proxy-agent/index.d.ts

@@ -1,6 +1,7 @@
 // Type definitions for http-proxy-agent 2.0
 // Project: https://github.com/TooTallNate/node-http-proxy-agent
 // Definitions by: mrmlnc <https://github.com/mrmlnc>
+//                 steprescott <https://github.com/steprescott>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 /// <reference types="node"/>
@@ -10,6 +11,9 @@ import { Url } from 'url';
 
 declare class HttpProxyAgent extends Agent {
     constructor(options: string | Url);
+
+    proxy: Url;
+    secureProxy: boolean;
 }
 
 export = HttpProxyAgent;