Accepting and declining invites

Hook up accept and decline buttons in the invites UI. Accept
will attempt to accept and then navigate to the room; decline
shows a confirmation dialog.

Fixes #106

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/room/MatrixRoom.kt

@@ -23,7 +23,7 @@ import io.element.android.libraries.matrix.api.timeline.MatrixTimeline
 import kotlinx.coroutines.flow.Flow
 import java.io.Closeable
 
-interface MatrixRoom: Closeable {
+interface MatrixRoom : Closeable {
     val roomId: RoomId
     val name: String?
     val bestName: String
@@ -36,7 +36,7 @@ interface MatrixRoom: Closeable {
     val isDirect: Boolean
     val isPublic: Boolean
 
-    suspend fun members() : List<RoomMember>
+    suspend fun members(): List<RoomMember>
 
     suspend fun memberCount(): Int
 
@@ -63,4 +63,8 @@ interface MatrixRoom: Closeable {
     suspend fun redactEvent(eventId: EventId, reason: String? = null): Result<Unit>
 
     suspend fun leave(): Result<Unit>
+
+    suspend fun acceptInvitation(): Result<Unit>
+
+    suspend fun rejectInvitation(): Result<Unit>
 }