speaker highlighting added on sample-app (#125) (#126)

* speaker highlighting added on sample-app (#125)

* Update ParticipantItem.kt

 package io.livekit.android.sample
 
+
+import android.graphics.Color
+import android.graphics.drawable.GradientDrawable
 import android.view.View
 import com.github.ajalt.timberkt.Timber
 import com.xwray.groupie.viewbinding.BindableItem
@@ -45,6 +48,15 @@ class ParticipantItem(
             }
         }
         coroutineScope?.launch {
+            participant::isSpeaking.flow.collect { isSpeaking ->
+                if (isSpeaking) {
+                    showFocus(viewBinding)
+                } else {
+                    hideFocus(viewBinding)
+                }
+            }
+        }
+        coroutineScope?.launch {
             participant::audioTracks.flow
                 .flatMapLatest { tracks ->
                     val audioTrack = tracks.firstOrNull()?.first
@@ -153,4 +165,20 @@ private fun View.visibleOrInvisible(visible: Boolean) {
     } else {
         View.INVISIBLE
     }
-}
\ No newline at end of file
+}
+
+private fun showFocus(binding: ParticipantItemBinding) {
+    val border = GradientDrawable()
+    border.setColor(Color.BLUE)
+    border.setStroke(8, -0x1000000)
+    binding.root.setPadding(16,16,16,16)
+    binding.root.background = border
+}
+
+private fun hideFocus(binding: ParticipantItemBinding) {
+    val border = GradientDrawable()
+    border.setColor(Color.TRANSPARENT)
+    border.setStroke(0, -0x1000000)
+    binding.root.setPadding(0,0,0,0)
+    binding.root.background = border
+}