The package imgui-sfml provides CMake targets:

    find_package(imgui CONFIG REQUIRED)
    find_package(SFML CONFIG REQUIRED COMPONENTS graphics system window)
    find_package(ImGui-SFML CONFIG REQUIRED)
    target_link_libraries(main PRIVATE
        imgui::imgui
        sfml-graphics sfml-system sfml-window
        ImGui-SFML::ImGui-SFML
    )
