[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/view_port_i.h

@@ -1,3 +1,8 @@
+/**
+ * @file view_port_i.h
+ * GUI: internal ViewPort API
+ */
+
 #pragma once
 
 #include "gui_i.h"
@@ -18,23 +23,29 @@ struct ViewPort {
     void* input_callback_context;
 };
 
-/*
- * Set GUI reference.
+/** Set GUI reference.
+ *
  * To be used by GUI, called upon view_port tree insert
- * @param gui - gui instance pointer.
+ *
+ * @param      view_port  ViewPort instance
+ * @param      gui        gui instance pointer
  */
 void view_port_gui_set(ViewPort* view_port, Gui* gui);
 
-/*
- * Process draw call. Calls draw callback.
+/** Process draw call. Calls draw callback.
+ *
  * To be used by GUI, called on tree redraw.
- * @param canvas - canvas to draw at.
+ *
+ * @param      view_port  ViewPort instance
+ * @param      canvas     canvas to draw at
  */
 void view_port_draw(ViewPort* view_port, Canvas* canvas);
 
-/*
- * Process input. Calls input callbac
+/** Process input. Calls input callback.
+ *
  * To be used by GUI, called on input dispatch.
- * @param event - pointer to input event.
+ *
+ * @param      view_port  ViewPort instance
+ * @param      event      pointer to input event
  */
 void view_port_input(ViewPort* view_port, InputEvent* event);