benchmark: add benchmark for EventTarget add and remove

Refs: nodejs/performance#60

benchmark/events/eventtarget-add-remove.js

@@ -0,0 +1,26 @@
+'use strict';
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  n: [1e6],
+  nListener: [5, 10],
+});
+
+function main({ n, nListener }) {
+  const target = new EventTarget();
+  const listeners = [];
+  for (let k = 0; k < nListener; k += 1)
+    listeners.push(() => {});
+
+  bench.start();
+  for (let i = 0; i < n; i += 1) {
+    const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
+    for (let k = listeners.length; --k >= 0;) {
+      target.addEventListener(dummy, listeners[k]);
+    }
+    for (let k = listeners.length; --k >= 0;) {
+      target.removeEventListener(dummy, listeners[k]);
+    }
+  }
+  bench.end(n);
+}