Async temperature usermod (#1178)

* Change Temperature usermod to use async reading to avoid blocking

* Fix comparison on wait time

* Add

* Simplify logic in the loop method

* Optimize calls to minimize latency, inform user how long till first measurement

* disable usermod if sensor not found

* Added debug statements on init, update readme

* fix spelling error of celsius

wled00/usermods_list.cpp

@@ -10,7 +10,9 @@
  * \/ \/ \/
  */
 //#include "usermod_v2_example.h"
-//#include "usermod_temperature.h"
+#ifdef USERMOD_DALLASTEMPERATURE
+#include "../usermods/Temperature/usermod_temperature.h"
+#endif
 //#include "usermod_v2_empty.h"
 
 void registerUsermods()
@@ -21,6 +23,8 @@ void registerUsermods()
    * \/ \/ \/
    */
   //usermods.add(new MyExampleUsermod());
-  //usermods.add(new UsermodTemperature());
+  #ifdef USERMOD_DALLASTEMPERATURE
+  usermods.add(new UsermodTemperature());
+  #endif
   //usermods.add(new UsermodRenameMe());
 }