🐛 Make the SMBus mutex thread background so that it doesn't prevent t…

…he service from stopping.

Exo.Core/AsyncGlobalMutex.cs

@@ -165,7 +165,7 @@ public static AsyncGlobalMutex Get(string name)
 	private AsyncGlobalMutex(string mutexName)
 	{
 		_mutex = new(false, mutexName);
-		_thread = new(MutexThread);
+		_thread = new(MutexThread) { IsBackground = true };
 		_pendingTaskList = new();
 		_waitQueue = new();
 		_manualResetEvent = new(false);