Floating point comparison warning

[DarkWingMcQuack]

When building with gcc-12 and the -Wfloat-equal flag the following warning is raised:

/home/x/project/build/deps/cli11/include/CLI/TypeTools.hpp: In function ‘std::string CLI::detail::sum_string_vector(const std::vector<std::__cxx11::basic_string<char> >&)’:
/home/x/project/build/deps/cli11/include/CLI/TypeTools.hpp:1549:16: warning: comparing floating-point with ‘==’ or ‘!=’ is unsafe [-Wfloat-equal]
 1549 |            val == static_cast<std::int64_t>(val)) {
      |            ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~