missing include

[Carmelo908]

trafficstars

Environment

toml++ version and/or commit hash:
3.4.0

Compiler: g++ 13.1.0

C++ standard mode:
C++17

Target arch:
x64

Library configuration overrides:
None

Relevant compilation flags:
None

Describe the bug

I installed the library with vcpkg and added the toolchain file with CMake, then tried to compile my program and I got an error from the compiler:

.../vcpkg_installed/x64-linux/include/toml++/impl/date_time.hpp:337:17: error: ‘optional’ does not name a type

I went to the file and added "#include " at the top. it worked and I could compile