perf_hooks: add initiatorType getter

PR-URL: #43593
Refs: https://w3c.github.io/resource-timing/#dfn-initiator-type
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>

Author: RafaelGSS

lib/internal/perf/resource_timing.js

@@ -46,6 +46,10 @@ class InternalPerformanceResourceTiming extends InternalPerformanceEntry {
     return this[kTimingInfo].endTime - this[kTimingInfo].startTime;
   }
 
+  get initiatorType() {
+    return this[kInitiatorType];
+  }
+
   get workerStart() {
     return this[kTimingInfo].finalServiceWorkerStartTime;
   }

test/parallel/test-perf-hooks-resourcetiming.js

@@ -134,6 +134,7 @@ function createTimingInfo({
   assert.ok(typeof resource.cacheMode === 'undefined', 'cacheMode does not have a getter');
   assert.strictEqual(resource.startTime, timingInfo.startTime);
   assert.strictEqual(resource.duration, 0);
+  assert.strictEqual(resource.initiatorType, initiatorType);
   assert.strictEqual(resource.workerStart, 0);
   assert.strictEqual(resource.redirectStart, 0);
   assert.strictEqual(resource.redirectEnd, 0);