Make task priority configurable

[pull request 98](me-no-dev#98)

Author: serek4

src/AsyncTCP.cpp

@@ -218,7 +218,7 @@ static bool _start_async_task(){
         return false;
     }
     if(!_async_service_task_handle){
-        xTaskCreateUniversal(_async_service_task, "async_tcp", CONFIG_ASYNC_TCP_STACK, NULL, 3, &_async_service_task_handle, CONFIG_ASYNC_TCP_RUNNING_CORE);
+        xTaskCreateUniversal(_async_service_task, "async_tcp", CONFIG_ASYNC_TCP_STACK, NULL, CONFIG_ASYNC_TCP_TASK_PRIORITY, &_async_service_task_handle, CONFIG_ASYNC_TCP_RUNNING_CORE);
         if(!_async_service_task_handle){
             return false;
         }

src/AsyncTCP.h

@@ -38,6 +38,9 @@ extern "C" {
 #ifndef CONFIG_ASYNC_TCP_STACK
 #define CONFIG_ASYNC_TCP_STACK 8192 * 2
 #endif
+#ifndef CONFIG_ASYNC_TCP_TASK_PRIORITY
+#define CONFIG_ASYNC_TCP_TASK_PRIORITY 3
+#endif
 #ifndef CONFIG_ASYNC_TCP_QUEUE_SIZE
 #define CONFIG_ASYNC_TCP_QUEUE_SIZE 32
 #endif