doc: add missing documentation for PerformanceObserver.prototype.takeRecords()

Author: skyclouds2001

doc/api/perf_hooks.md

@@ -1339,6 +1339,14 @@ for (let n = 0; n < 3; n++)
   performance.mark(`test${n}`);
 ```
 
+### `performanceObserver.takeRecords()`
+
+<!-- YAML
+added: v16.0.0
+-->
+
+Gets the current list of {PerformanceEntry} objects stored in the performance observer, emptying it out.
+
 ## Class: `PerformanceObserverEntryList`
 
 <!-- YAML