docs: improve comment [skip ci]

Author: posva

docs/content/1.guide/12.in-page-channel.md

@@ -117,7 +117,8 @@ const panelChannel = connectPanelChannel<MyChannelProtocol>({
 })
 
 const offFlash = panelChannel.on('flash', message => showFlash(message))
-panelChannel.emit('highlight', '.hero') // received by the page-script endpoint
+// defined and received by the page-script endpoint
+panelChannel.emit('highlight', '.hero')
 const size = await panelChannel.call('measure', '.hero')
 await panelChannel.call('reset')