[FL-1906] Documentation: add Doxyfile, prepare sources for doxygen. (#741)

* Documentation: add Doxyfile, prepare sources for doxygen.

* Update ReadMe and remove obsolete CLA

* Add contribution guide

* Contributing: update text

* Correct spelling

applications/gui/modules/empty_screen.h

@@ -1,26 +1,38 @@
+/**
+ * @file empty_screen.h
+ * GUI: EmptyScreen view module API
+ */
+
 #pragma once
+
 #include <gui/view.h>
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/* Empty screen anonymous structure */
+/** Empty screen anonymous structure */
 typedef struct EmptyScreen EmptyScreen;
 
-/* Allocate and initialize empty screen
+/** Allocate and initialize empty screen
+ *
  * This empty screen used to ask simple questions like Yes/
+ *
+ * @return     EmptyScreen instance
  */
 EmptyScreen* empty_screen_alloc();
 
-/* Deinitialize and free empty screen
- * @param empty_screen - Empty screen instance
+/** Deinitialize and free empty screen
+ *
+ * @param      empty_screen  Empty screen instance
  */
 void empty_screen_free(EmptyScreen* empty_screen);
 
-/* Get empty screen view
- * @param empty_screen - Empty screen instance
- * @return View instance that can be used for embedding
+/** Get empty screen view
+ *
+ * @param      empty_screen  Empty screen instance
+ *
+ * @return     View instance that can be used for embedding
  */
 View* empty_screen_get_view(EmptyScreen* empty_screen);