🐛 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);