Thread decoration: add and branch isThreaded method

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/item/event/EventContent.kt

@@ -32,6 +32,7 @@ data class MessageContent(
     val body: String,
     val inReplyTo: InReplyTo?,
     val isEdited: Boolean,
+    val isThreaded: Boolean,
     val type: MessageType?
 ) : EventContent
 

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/timeline/item/event/EventTimelineItem.kt

@@ -40,6 +40,11 @@ data class EventTimelineItem(
     fun inReplyTo(): InReplyTo? {
         return (content as? MessageContent)?.inReplyTo
     }
+
+    fun isThreaded(): Boolean {
+        return (content as? MessageContent)?.isThreaded ?: false
+    }
+
     fun hasNotLoadedInReplyTo(): Boolean {
         val details = inReplyTo()
         return details is InReplyTo.NotLoaded