UI: message field take focus

When open conversation make message field active

Change-Id: I668b16001f8efa4eda2913f2ad46439a98412ba0
Reviewed-by: Anthony Léonard <anthony.leonard@savoirfairelinux.com>

src/ConversationVC.mm

@@ -254,6 +254,7 @@
     if (auto txtRecording = selectedContactMethod->textRecording()) {
         messagesViewVC.delegate = self;
         [messagesViewVC setUpViewWithModel:txtRecording->instantMessagingModel()];
+        [self.view.window makeFirstResponder:messageField];
     }
 }