[https-proxy-agent] Emit "proxyConnect" event on Agent (#156)

Closes #153.

Author: TooTallNate

.changeset/perfect-terms-tie.md

@@ -0,0 +1,5 @@
+---
+'https-proxy-agent': minor
+---
+
+Emit "proxyConnect" event on Agent instance

packages/https-proxy-agent/src/index.ts

@@ -132,6 +132,7 @@ export class HttpsProxyAgent<Uri extends string> extends Agent {
 
 		const { connect, buffered } = await proxyResponsePromise;
 		req.emit('proxyConnect', connect);
+		this.emit('proxyConnect', connect, req);
 
 		if (connect.statusCode === 200) {
 			req.once('socket', resume);

packages/https-proxy-agent/test/test.ts

@@ -126,7 +126,11 @@ describe('HttpsProxyAgent', () => {
 				rejectUnauthorized: false,
 			});
 
-			const res = await req(serverUrl, { agent });
+			const r = req(serverUrl, { agent });
+			const [connect] = await once(agent, 'proxyConnect');
+			expect(connect.statusCode).toEqual(200);
+			expect(connect.statusText).toEqual('Connection established');
+			const res = await r;
 			const body = await json(res);
 			assert.equal(serverUrl.host, body.host);
 		});