test: add test for process.stdin.setRawMode()

adds a basic test for process.stdin.setRawMode to ensure that the isRaw
property is properly changed

PR-URL: https://github.com/nodejs/node/pull/10037
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/pseudo-tty/stdin-setrawmode.js

@@ -0,0 +1,9 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+
+process.stdin.setRawMode(true);
+assert.strictEqual(process.stdin.isRaw, true);
+
+process.stdin.setRawMode(false);
+assert.strictEqual(process.stdin.isRaw, false);