[Room] Add getParticipants method

lib/src/Room.dart

@@ -515,6 +515,17 @@ class Room {
     return await client.store.loadParticipants(this);
   }
 
+  /// Returns all participants for this room. With lazy loading this
+  /// list may not be complete. User [requestParticipants] in this
+  /// case.
+  List<User> getParticipants() {
+    List<User> userList = [];
+    for (var entry in states.entries)
+      if (entry.value.type == EventTypes.RoomMember)
+        userList.add(entry.value.asUser);
+    return userList;
+  }
+
   /// Request the full list of participants from the server. The local list
   /// from the store is not complete if the client uses lazy loading.
   Future<List<User>> requestParticipants() async {

test/Room_test.dart

@@ -225,6 +225,21 @@ void main() {
       expect(resp, {});
     });
 
+    test("getParticipants", () async {
+      room.states["@alice:test.abc"] = RoomState(
+          senderId: "@alice:test.abc",
+          typeKey: "m.room.member",
+          roomId: room.id,
+          room: room,
+          eventId: "12345",
+          time: ChatTime.now(),
+          content: {"displayname": "alice"},
+          stateKey: "@alice:test.abc");
+      final List<User> userList = room.getParticipants();
+      expect(userList.length, 1);
+      expect(userList[0].displayName, "alice");
+    });
+
     test("addToDirectChat", () async {
       final dynamic resp = await room.addToDirectChat("Testname");
       expect(resp, {});