[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/scene_manager.h

@@ -1,14 +1,18 @@
+/**
+ * @file scene_manager.h
+ * GUI: SceneManager API
+ */
+
 #pragma once
 
+#include <stdint.h>
+#include <stdbool.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <stdint.h>
-#include <stdbool.h>
-
-/** Scene Manager events type
- */
+/** Scene Manager events type */
 typedef enum {
     SceneManagerEventTypeCustom,
     SceneManagerEventTypeBack,
@@ -44,86 +48,110 @@ typedef struct {
 typedef struct SceneManager SceneManager;
 
 /** Set Scene state
- * @param scene_manager SceneManager instance
- * @param scene_id Scene ID
- * @param state Scene new state
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      scene_id       Scene ID
+ * @param      state          Scene new state
  */
 void scene_manager_set_scene_state(SceneManager* scene_manager, uint32_t scene_id, uint32_t state);
 
 /** Get Scene state
- * @param scene_manager SceneManager instance
- * @param scene_id Scene ID
- * @return Scene state
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      scene_id       Scene ID
+ *
+ * @return     Scene state
  */
 uint32_t scene_manager_get_scene_state(SceneManager* scene_manager, uint32_t scene_id);
 
 /** Scene Manager allocation and configuration
+ *
  * Scene Manager allocates all scenes internally
- * @param app_scene_handlers SceneManagerHandlers instance
- * @param context context to be set on Scene handlers calls
- * @return SceneManager instance
+ *
+ * @param      app_scene_handlers  SceneManagerHandlers instance
+ * @param      context             context to be set on Scene handlers calls
+ *
+ * @return     SceneManager instance
  */
 SceneManager* scene_manager_alloc(const SceneManagerHandlers* app_scene_handlers, void* context);
 
 /** Free Scene Manager with allocated Scenes
- * @param scene_manager SceneManager instance
+ *
+ * @param      scene_manager  SceneManager instance
  */
 void scene_manager_free(SceneManager* scene_manager);
 
 /** Custom event handler
+ *
  * Calls Scene event handler with Custom event parameter
- * @param scene_manager SceneManager instance
- * @param custom_event Custom event code
- * @return true if event was consumed, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      custom_event   Custom event code
+ *
+ * @return     true if event was consumed, false otherwise
  */
 bool scene_manager_handle_custom_event(SceneManager* scene_manager, uint32_t custom_event);
 
 /** Back event handler
+ *
  * Calls Scene event handler with Back event parameter
- * @param scene_manager SceneManager instance
- * @return true if event was consumed, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ *
+ * @return     true if event was consumed, false otherwise
  */
 bool scene_manager_handle_back_event(SceneManager* scene_manager);
 
 /** Tick event handler
+ *
  * Calls Scene event handler with Tick event parameter
- * @param scene_manager SceneManager instance
- * @return true if event was consumed, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ * @return     true if event was consumed, false otherwise
  */
 void scene_manager_handle_tick_event(SceneManager* scene_manager);
 
 /** Add and run next Scene
- * @param scene_manager SceneManager instance
- * @param next_scene_id next Scene ID
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      next_scene_id  next Scene ID
  */
 void scene_manager_next_scene(SceneManager* scene_manager, uint32_t next_scene_id);
 
 /** Run previous Scene
- * @param scene_manager SceneManager instance
- * @return true if previous scene was found, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ *
+ * @return     true if previous scene was found, false otherwise
  */
 bool scene_manager_previous_scene(SceneManager* scene_manager);
 
 /** Search previous Scene
- * @param scene_manager SceneManager instance
- * @param scene_id Scene ID
- * @return true if previous scene was found, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      scene_id       Scene ID
+ *
+ * @return     true if previous scene was found, false otherwise
  */
 bool scene_manager_has_previous_scene(SceneManager* scene_manager, uint32_t scene_id);
 
 /** Search and switch to previous Scene
- * @param scene_manager SceneManager instance
- * @param scene_id Scene ID
- * @return true if previous scene was found, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      scene_id       Scene ID
+ *
+ * @return     true if previous scene was found, false otherwise
  */
 bool scene_manager_search_and_switch_to_previous_scene(
     SceneManager* scene_manager,
     uint32_t scene_id);
 
 /** Clear Scene stack and switch to another Scene
- * @param scene_manager SceneManager instance
- * @param scene_id Scene ID
- * @return true if previous scene was found, false otherwise
+ *
+ * @param      scene_manager  SceneManager instance
+ * @param      scene_id       Scene ID
+ *
+ * @return     true if previous scene was found, false otherwise
  */
 bool scene_manager_search_and_switch_to_another_scene(
     SceneManager* scene_manager,