Add support for nxxm.

[nxxm](https://nxxm.github.io)

CMakeLists.txt

@@ -6,5 +6,115 @@ project(ftxui
 
 enable_testing()
 
-add_subdirectory(ftxui)
+cmake_minimum_required(VERSION 3.0)
+find_package(Threads)
+
+add_library(screen
+  src/ftxui/screen/box.cpp
+  src/ftxui/screen/screen.cpp
+  src/ftxui/screen/string.cpp
+  src/ftxui/screen/terminal.cpp
+)
+
+add_library(dom
+  src/ftxui/dom/blink.cpp
+  src/ftxui/dom/bold.cpp
+  src/ftxui/dom/border.cpp
+  src/ftxui/dom/color.cpp
+  src/ftxui/dom/composite_decorator.cpp
+  src/ftxui/dom/dbox.cpp
+  src/ftxui/dom/dim.cpp
+  src/ftxui/dom/flex.cpp
+  src/ftxui/dom/frame.cpp
+  src/ftxui/dom/gauge.cpp
+  src/ftxui/dom/graph.cpp
+  src/ftxui/dom/hbox.cpp
+  src/ftxui/dom/hflow.cpp
+  src/ftxui/dom/inverted.cpp
+  src/ftxui/dom/node.cpp
+  src/ftxui/dom/node_decorator.cpp
+  src/ftxui/dom/paragraph.cpp
+  src/ftxui/dom/separator.cpp
+  src/ftxui/dom/size.cpp
+  src/ftxui/dom/spinner.cpp
+  src/ftxui/dom/text.cpp
+  src/ftxui/dom/underlined.cpp
+  src/ftxui/dom/util.cpp
+  src/ftxui/dom/vbox.cpp
+)
+
+add_library(component
+  src/ftxui/component/checkbox.cpp
+  src/ftxui/component/component.cpp
+  src/ftxui/component/container.cpp
+  src/ftxui/component/event.cpp
+  src/ftxui/component/input.cpp
+  src/ftxui/component/menu.cpp
+  src/ftxui/component/radiobox.cpp
+  src/ftxui/component/screen_interactive.cpp
+  src/ftxui/component/toggle.cpp
+)
+
+target_link_libraries(dom PUBLIC screen)
+target_link_libraries(component PUBLIC dom)
+target_link_libraries(component PUBLIC Threads::Threads)
+
+foreach(lib screen dom component)
+  target_include_directories(${lib}
+    PUBLIC
+      $<INSTALL_INTERFACE:include>    
+      $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+    PRIVATE src
+  )
+  target_compile_features(${lib} PUBLIC cxx_std_17)
+  target_compile_options(${lib} PRIVATE -Wall)
+endforeach()
+
+include(GNUInstallDirs)
+install(TARGETS screen dom component
+    EXPORT ftxui-export
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}/ftxui/
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}/ftxui/
+)
+
+install(DIRECTORY include/ftxui DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+
+include(CMakePackageConfigHelpers)
+write_basic_package_version_file(
+  ftxui-config.cmake
+  VERSION ${PACKAGE_VERSION}
+  COMPATIBILITY AnyNewerVersion
+)
+
+install(EXPORT ftxui-export
+  FILE ftxui-targets.cmake
+	NAMESPACE ftxui::
+	DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/ftxui
+)
+
+# Note: For gtest, please follow:
+# https://stackoverflow.com/questions/24295876/cmake-cannot-find-a-googletest-required-library
+find_package(GTest)
+if (GTEST_FOUND AND THREADS_FOUND)
+  add_executable(dom_tests
+    tests/gauge_test.cpp
+    tests/hbox_test.cpp
+    tests/text_test.cpp
+    tests/vbox_test.cpp
+  )
+
+  target_link_libraries(dom_tests
+    PRIVATE dom
+    PRIVATE Threads::Threads
+    PRIVATE ${GTEST_BOTH_LIBRARIES}
+  )
+
+  target_include_directories(dom_tests
+    PRIVATE ${GTest_INCLUDE_DIRS}
+  )
+  gtest_discover_tests(dom_tests)
+  add_test(dom_tests dom_tests)
+
+endif()
+
 add_subdirectory(examples)