Rename library for vcpkg. (#140)

Instead of putting the archive as:
- <lib_dir>/ftxui/libcomponent.a
- <lib_dir>/ftxui/libdom.a
- <lib_dir>/ftxui/libscreen.a

Use:
- <lib_dir>/libftxui-component.a
- <lib_dir>/libftxui-dom.a
- <lib_dir>/libftxui-screen.a

This fixes an issue users have with VCPKG.

See:
https://github.com/microsoft/vcpkg/issues/16327#issuecomment-868942370

cmake/ftxui_install.cmake

@@ -1,8 +1,8 @@
 include(GNUInstallDirs)
 install(TARGETS screen dom component
     EXPORT ftxui-export
-    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}/ftxui/
-    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}/ftxui/
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
 )
 
 install(DIRECTORY include/ftxui DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})

cmake/ftxui_set_options.cmake

@@ -1,4 +1,7 @@
 function(ftxui_set_options library)
+  set_target_properties(${library} PROPERTIES PREFIX "ftxui-")
+
+
   target_include_directories(${library}
     PUBLIC
       $<INSTALL_INTERFACE:include>