Add modules support (#1015)

Add experimental C++20 module suppport.
Co-authored-by: ArthurSonzogni <sonzogniarthur@gmail.com>

examples/component/scrollbar.cpp

@@ -3,6 +3,7 @@
 // the LICENSE file.
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/screen_interactive.hpp>
+#include <string>
 
 using namespace ftxui;
 

examples/component/window.cpp

@@ -3,6 +3,7 @@
 // the LICENSE file.
 #include <ftxui/component/component.hpp>
 #include <ftxui/component/screen_interactive.hpp>
+#include <string>
 
 using namespace ftxui;