Improve documentation (#1058)

* Remove @ingroup from class member definitions
* Add the documentation for every public classes.

include/ftxui/screen/box.hpp

@@ -6,6 +6,13 @@
 
 namespace ftxui {
 
+/// @brief Box is a structure that represents a rectangular area in a 2D space.
+///
+/// It is defined by its minimum and maximum coordinates along the x and y axes.
+/// Note that the coordinates are inclusive, meaning that the box includes both
+/// the minimum and maximum values.
+/// 
+/// @ingroup screen
 struct Box {
   int x_min = 0;
   int x_max = 0;

include/ftxui/screen/color.hpp

@@ -15,7 +15,9 @@
 
 namespace ftxui {
 
-/// @brief A class representing terminal colors.
+/// @brief Color is a class that represents a color in the terminal user
+/// interface.
+///
 /// @ingroup screen
 class Color {
  public:

include/ftxui/screen/color_info.hpp

@@ -9,6 +9,10 @@
 
 namespace ftxui {
 
+/// @brief ColorInfo is a structure that contains information about the terminal
+/// color palette.
+///
+/// @ingroup screen
 struct ColorInfo {
   const char* name;
   uint8_t index_256;

include/ftxui/screen/terminal.hpp

@@ -5,6 +5,9 @@
 #define FTXUI_SCREEN_TERMINAL_HPP
 
 namespace ftxui {
+
+/// @brief Dimensions is a structure that represents the size of the terminal
+/// @ingroup screen
 struct Dimensions {
   int dimx;
   int dimy;
@@ -14,6 +17,9 @@ namespace Terminal {
 Dimensions Size();
 void SetFallbackSize(const Dimensions& fallbackSize);
 
+/// @brief Color is an enumeration that represents the color support of the
+/// terminal.
+/// @ingroup screen
 enum Color {
   Palette1,
   Palette16,