Various improvements (#21)

* T-Deck stability and naming improvements

* allow main task to clean itself up

* remove unused includes

* various lvgl improvements

* added docs

app-sim/src/lvgl_task.h

@@ -6,8 +6,9 @@
 extern "C" {
 #endif
 
-bool lvgl_is_ready();
-void lvgl_interrupt();
+void lvgl_task_start();
+bool lvgl_task_is_running();
+void lvgl_task_interrupt();
 
 #ifdef __cplusplus
 }