Apply suggestions from code review

From @hoch

Co-authored-by: Hongchan Choi <hongchan.choi@gmail.com>

Author: Hernqvist

index.bs

@@ -11565,7 +11565,7 @@ Audio underruns (also commonly called glitches) are gaps in the audio
 playout which occur when the audio pipeline cannot deliver audio on time.
 Underruns (often manifesting as audible "clicks" in the playout) are bad
 for the user experience, so if any of these occur it
-can be useful for the application to be able to detect this and possibly
+can be useful for the application to be able to detect them and possibly
 take some action to improve the playout.
 
 {{AudioPlayoutStats}} is a dedicated object for audio stats reporting;
@@ -11580,9 +11580,9 @@ Underruns are defined in terms of [=underrun frames=] and [=underrun events=]:
     This happens when the playout path fails to provide audio frames
     to the output device on time, in which case underrun frames will be played (underrun frames are typically silence).
     This typically only happens if the pipeline is underperforming.
-    This includes underrun situations that happen for reasons unrelated to WebAudio/{{AudioWorklet}}s.</li>
+    This includes underrun situations that happen for reasons unrelated to WebAudio/{{AudioWorklet}}s.
 - When an [=underrun frame=] is played after a non-underrun frame, we consider this an <dfn>underrun event</dfn>.
-    That is, multiple consecutive [=underrun frames=] will count as a single [=underrun event=].</li>
+    That is, multiple consecutive [=underrun frames=] will count as a single [=underrun event=].
 
 <pre class="idl">
 [Exposed=Window, SecureContext]
@@ -11754,21 +11754,21 @@ One site could transmit information by intentionally causing audio glitches
 (by causing very high CPU usage, for example) while the other site
 could detect these glitches.
 <h5 id="AudioPlayoutStats-mitigations">Mitigations</h5>
-To inihibit the usage of such a covert channel, the API implements these mitigations.
+To inhibit the usage of such a covert channel, the API implements these mitigations.
 - The values returned by the API should not be updated more than once per second.
 - The api should be restricted to sites fulfill at least one of the following criteria:
     1. The site has obtained <a href="https://w3c.github.io/mediacapture-main/#dom-mediadevices-getusermedia">getUserMedia</a> permission.
 
         Note: The reasoning is that if a site has obtained <a href="https://w3c.github.io/mediacapture-main/#dom-mediadevices-getusermedia">getUserMedia</a> permission, it can receive glitch information or communicate efficiently through use of the microphone, making access to the information provided by {{AudioPlayoutStats}} redundant. These options include detecting glitches through gaps in the microphone signal, or communicating using human-inaudible sine waves. If microphone access is ever made safer in this regard, this condition should be reconsidered.
     1. The document is [=Document/fully active=] and its [=Document/visibility state=] is `"visible"`.
 
-        Note: Assuming that neither cooperating site has microphone permission, this criteria ensures that the site that receives the covert signal must be visible, restricting the conditions under which the covert channel can be used. It makes it impossible for sites to communicate with each other using the covert channel while not visible.
+        Note: Assuming that neither cooperating site has microphone permission, this criterion ensures that the site that receives the covert signal must be visible, restricting the conditions under which the covert channel can be used. It makes it impossible for sites to communicate with each other using the covert channel while not visible.
 
 <h4>Usage example</h4>
 This example shows how the {{AudioPlayoutStats}} can be used to calculate audio underrun and latency statistics,
 and what the statistics might be used for.
 <pre line-numbers class="example" highlight="js">
-var oldTotalDuration = audioContext.playoutStats.totalDuration;
+let oldTotalDuration = audioContext.playoutStats.totalDuration;
 var oldUnderrunDuration = audioContext.playoutStats.underrunDuration;
 var oldUnderrunEvents = audioContext.playoutStats.underrunEvents;
 audioContext.playoutStats.resetLatency();