bug: volume resetting when adding a new chat

Forgot to read the value.

closes #109

Author: ProgrammingByPermutation

src/TwitchStreamingTools/ViewModels/Pages/ChatViewModel.cs

@@ -169,7 +169,7 @@ from user in _selectedTwitchChatNames
         OutputDevice = Configuration.GetDefaultAudioDevice(),
         TtsOn = true,
         TtsVoice = Configuration.GetDefaultTtsVoice(),
-        TtsVolume = 50
+        TtsVolume = Configuration.GetDefaultTtsVolume() ?? 50u
       }).ToList();
 
     _configuration.WriteConfiguration();
@@ -194,7 +194,7 @@ from user in _selectedTwitchChatNames
         OutputDevice = Configuration.GetDefaultAudioDevice(),
         TtsOn = true,
         TtsVoice = Configuration.GetDefaultTtsVoice(),
-        TtsVolume = 50
+        TtsVolume = Configuration.GetDefaultTtsVolume() ?? 50u
       }).ToList();
 
     _configuration.WriteConfiguration();